CLN: Move test_intersect_str_dates from tests/indexes/test_range.py to test_base.py
- [X] closes #17362
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

It doesn't seem like `test_intersect_str_dates` has anything to do with `RangeIndex`, so I've moved it from `test_range.py` to `test_base.py`.