bpo-45662: Fix the repr of InitVar with a type alias to the built-in class (GH-29291)

For example, InitVar[list[int]].
(cherry picked from commit 1fd4de5bddbbf2a97cdbac4d298c89e1156bdc6c)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>