Run mypy over test/test_utils.py (#50278)
Summary:
_resubmission of gh-49654, which was reverted due to a cross-merge conflict_
This caught one incorrect annotation in `cpp_extension.load`.
xref gh-16574.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50278
Reviewed By: walterddr
Differential Revision: D25865278
Pulled By: ezyang
fbshipit-source-id: 25489191628af5cf9468136db36f5a0f72d9d54d
