[3.11] Improve assert_type phrasing (GH-104081) (#104084)

Improve assert_type phrasing (GH-104081)

I'd like to make the fact that this does nothing at runtime
really obvious, since I suspect this is unintuitive for users who are
unfamiliar with static type checking.

I thought of this because of
https://discuss.python.org/t/add-arg-check-type-to-types/26384
wherein I'm skeptical that the user really did want `assert_type`.
(cherry picked from commit 82ba6ce303d04a7b21034e38d220e23ca9f1dc0a)

Co-authored-by: Shantanu <12621235+hauntsaninja@users.noreply.github.com>