gh-96130: Rephrase use of "typecheck" verb for clarity (GH-98144)

I'm sympathetic to the issue report, especially in case this helps
clarify to new users that Python itself does not do type checking at runtime
(cherry picked from commit ed6344eed043eaaa41d11c1176c25aa79de64ef4)

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