commonmark is archived and deprecated

[Avasam]

When reviewing #13724, I noticed that the commonmark repository is archived since March 25th, 2022
https://github.com/readthedocs/commonmark.py
And read readthedocs/commonmark.py#308

It's also marked as deprecated in favor of https://github.com/executablebooks/markdown-it-py (which is also py.typed !)

Since the previously linked typeshed PR, our commonmark stubs are pretty complete, spare a few dict[str, Any] that could be private stubs-only TypedDict. (but I doubt it's worth the effort)

I propose we remove the stubs as per our Third-party library removal policy using the no_longer_updated field and an extra description pushing users to https://pypi.org/project/markdown-it-py/

This will also positively affect #9550

[srittau]

I forced an update: https://pypi.org/project/types-commonmark/