[doc] Leverage the fact that the actual types can now be indexed for typing (GH-22340)

[doc] Leverage the fact that the actual types can now be indexed for typing (GH-22340)

This shows users that they can use the actual types. Using deprecated types is confusing.

This also prefers colections.abc.Sized instead of the alias typing.Sized. I guess the aliases were created to make it convenient to import all collections related types from the same place.

This should be backported to 3.9.

Automerge-Triggered-By: @gvanrossum
(cherry picked from commit d9ab95ff1fe81efdf70e545d536d9f6927d1ba81)

Co-authored-by: Andre Delfino <adelfino@gmail.com>