[3.11] Enhance TypedDict docs around required/optional keys (GH-109547) by miss-islington · Pull Request #109983 · python/cpython

@JelleZijlstra @miss-islington

As discussed in comments to pythonGH-109544, the semantics of this attribute
are somewhat confusing. Add a note explaining its limitations and
steering users towards __required_keys__ and __optional_keys__ instead.
(cherry picked from commit f49958c)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>