CLN: fix mypy errors in pandas/tests/extension/test_numpy.py #28926
- [ ] xref #28926 
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

does this also fix the errors in `pandas\tests\extension\test_sparse` Great thanks @lukasbk !