TST: Test inequality w/ complex dtypes (GH28050)
- [x] closes #28050
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

Whats new::
Add a test to `pandas/test/dtypes/test_dtypes.py`
