`test_unittest` failing due to `test/test_unittest/testmock/testthreadingmock` assuming threading exists

https://github.com/python/cpython/commit/d65b783b6966d233467a48ef633afb4aff9d5df8 via https://github.com/python/cpython/pull/16094 the culprit.


### Linked PRs
* gh-106366