gh-87961: Remove outdated notes from functions that aren't in the Limited API (GH-93581)

* Remove outdated notes from functions that aren't in the Limited API

Nowadays everything that *is* in the Limited API has a note added
automatically.
These notes could mislead people to think that these functions
could never be added to the limited API. Remove them.

* Also remove forgotten note on tp_vectorcall_offset not being finalized