sagemathgh-37740: Disable most documentation notifications on GitHub
    
Previously, the documentation comment on GitHub would be removed and
then recreated whenever there is a change to a PR which creates
notification emails and to some feels like it's polluting their GitHub
inbox.

Here, we change this behavior so that only the initial build of the
documentation causes such a notification. Further updates to the
documentation do update the links in the comment but do not trigger a
notification.

This is meant as an alternative to sagemath#37387. See sagemath#37739 for futher ideas
about a smarter behavior here.

An actual preview of the result can be seen here:
saraedum#2

Note that the links on that PR do not work because my fork does not have
netlify credentials configured.

### 📝 Checklist

- [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.
- [x] I have created tests covering the changes; this is fairly hard to
test automatically. I'll test this manually if there is interest in
merging this.
- [x] I have updated the documentation accordingly; kind of, I updated
the PR checklist.
    
URL: sagemath#37740
Reported by: Julian Rüth
Reviewer(s): Dima Pasechnik, Julian Rüth, Kwankyu Lee

Remove excessive blank lines around INPUT, OUTPUT, EXAMPLES, and before
docstring ending """. (#2)

* Add some `except`s

For C-return-type functions that raise exceptions (and their heirs).

* Use `except?` for `_rank`

bump up external meson's minimal version for scipy