Describe the bug
Enum values are always shown in alphabetical order, regardless of the requested order in docfx.json.

To Reproduce
Steps to reproduce the behavior:

1. Add any of the following attempts to an existing docfx.json file:
   • "enumSortOrder": "declaringOrder"
   • "enumSortOrder": "DeclaringOrder"
   • "EnumSortOrder": "declaringOrder"
   • "EnumSortOrder": "DeclaringOrder"
2. Note that this property name is not allowed by the published schema at https://json.schemastore.org/docfx.json, but let's try to build the site anyway.
3. docfx docfx.json --serve

Expected behavior

1. Enum values should be shown in declaring order.
   • Alternatively, if the current version of the docfx tool doesn't recognize a property specified in the docfx.json file, or if it rejects the syntax of a property, it should output a warning on the command line when it builds the site.
2. https://json.schemastore.org/docfx.json should be maintained, so that editing a docfx.json file in a modern editor (Visual Studio) helps the author to find the right syntax without trial-and-error.
3. https://dotnet.github.io/docfx/reference/docfx-json-reference.html#enumsortorder should also be updated with the correct capitalization, whichever it is.

Context (please complete the following information):

• OS: Windows 10 Pro
• Docfx version:

>dotnet --version
8.0.200

>docfx --version
4.75.3+a5c719410037cc288c7adff010b1abf3c0f2e581

Additional context
This PR, merged August 2023:

• feat: option to sort enum member in declaring order #9093

...purports to fix this issue from December 2017:

• Option to not sort Enum values #2285