Expand on enum limitations

[samypr100]

Documentation

Encountered the python/mypy#14494 issue and it was suggested that we include it on the docs. This issue is an atttempt to expand on the documentation for this particular issue.

Linked PRs

• [docs] gh-101273: Expand enum documentation on limitations #101274

[ethanfurman]

Closing in favor of issue 103596.