sagemathgh-38549: Prepare sage for sphinx 8
    
This PR prepares sage for sphinx 8. An update for sage_autodoc.py is
needed and is provided in this PR.
The minimum known version of sphinx supporting the updated
sage_autodoc.py is 7.4.7. So, sphinx is updated from 7.3.7 (which is
known not to work) to 7.4.7.


### 📝 Checklist

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- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38549
Reported by: François Bissey
Reviewer(s):

sagemathgh-38619: Re-add py3.9 support to sage_autodoc.py
    
This PR corrects the fact the sage_autodoc.py changes needed for sphinx
8 dropped python 3.9 support. This is a consequence of the fact that
sphinx 8 has dropped python 3.9.
Since we still want to support python 3.9, some support has to be re-
introduced.
See sagemath#38549 (comment)
and after.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38619
Reported by: François Bissey
Reviewer(s):

sagemathgh-38627: Require weaker Sphinx dependency for sagelib
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The version constraint added in
sagemath#38549 broke the conda ci workflow
and added an unnecessarily strict version constraint for sphinx as a
dependency of sagelib (as opposed to sage-the-docs).

This is fixed by providing the old version constraint for sphinx in
`setup.cfg`, but with `v8` now allowed.

Alternatively, the stricter version constraint should only be added to
the sage-the-docs package.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38627
Reported by: Tobias Diez
Reviewer(s): François Bissey

sagemathgh-38619: Re-add py3.9 support to sage_autodoc.py
    
This PR corrects the fact the sage_autodoc.py changes needed for sphinx
8 dropped python 3.9 support. This is a consequence of the fact that
sphinx 8 has dropped python 3.9.
Since we still want to support python 3.9, some support has to be re-
introduced.
See sagemath#38549 (comment)
and after.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38619
Reported by: François Bissey
Reviewer(s):

sagemathgh-38627: Require weaker Sphinx dependency for sagelib
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The version constraint added in
sagemath#38549 broke the conda ci workflow
and added an unnecessarily strict version constraint for sphinx as a
dependency of sagelib (as opposed to sage-the-docs).

This is fixed by providing the old version constraint for sphinx in
`setup.cfg`, but with `v8` now allowed.

Alternatively, the stricter version constraint should only be added to
the sage-the-docs package.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38627
Reported by: Tobias Diez
Reviewer(s): François Bissey

sagemathgh-38627: Require weaker Sphinx dependency for sagelib
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The version constraint added in
sagemath#38549 broke the conda ci workflow
and added an unnecessarily strict version constraint for sphinx as a
dependency of sagelib (as opposed to sage-the-docs).

This is fixed by providing the old version constraint for sphinx in
`setup.cfg`, but with `v8` now allowed.

Alternatively, the stricter version constraint should only be added to
the sage-the-docs package.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38627
Reported by: Tobias Diez
Reviewer(s): François Bissey

sagemathgh-38619: Re-add py3.9 support to sage_autodoc.py
    
This PR corrects the fact the sage_autodoc.py changes needed for sphinx
8 dropped python 3.9 support. This is a consequence of the fact that
sphinx 8 has dropped python 3.9.
Since we still want to support python 3.9, some support has to be re-
introduced.
See sagemath#38549 (comment)
and after.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38619
Reported by: François Bissey
Reviewer(s): Kwankyu Lee

sagemathgh-38627: Require weaker Sphinx dependency for sagelib
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The version constraint added in
sagemath#38549 broke the conda ci workflow
and added an unnecessarily strict version constraint for sphinx as a
dependency of sagelib (as opposed to sage-the-docs).

This is fixed by providing the old version constraint for sphinx in
`setup.cfg`, but with `v8` now allowed.

Alternatively, the stricter version constraint should only be added to
the sage-the-docs package.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38627
Reported by: Tobias Diez
Reviewer(s): François Bissey

sagemathgh-38619: Re-add py3.9 support to sage_autodoc.py
    
This PR corrects the fact the sage_autodoc.py changes needed for sphinx
8 dropped python 3.9 support. This is a consequence of the fact that
sphinx 8 has dropped python 3.9.
Since we still want to support python 3.9, some support has to be re-
introduced.
See sagemath#38549 (comment)
and after.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38619
Reported by: François Bissey
Reviewer(s): Kwankyu Lee

sagemathgh-38627: Require weaker Sphinx dependency for sagelib
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

The version constraint added in
sagemath#38549 broke the conda ci workflow
and added an unnecessarily strict version constraint for sphinx as a
dependency of sagelib (as opposed to sage-the-docs).

This is fixed by providing the old version constraint for sphinx in
`setup.cfg`, but with `v8` now allowed.

Alternatively, the stricter version constraint should only be added to
the sage-the-docs package.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#38627
Reported by: Tobias Diez
Reviewer(s): François Bissey