TYP: Ignore remaining mypy errors for pandas\tests\*

[simonjayhawkins]

• closes Fix mypy errors for pandas\tests\* #28926
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

These are the only 3 errors outstanding in pandas\tests* that are stopping us closing #28926

pandas\conftest.py:301: error: List item 0 has incompatible type "Type[Index]"; expected "Type[PandasObject]"  [list-item]
pandas\tests\window\conftest.py:79: error: List item 0 has incompatible type "ParameterSet"; expected "Sequence[Collection[object]]"  [list-item]
pandas\tests\window\conftest.py:330: error: List item 15 has incompatible type "ParameterSet"; expected "Sequence[Collection[object]]"  [list-item]

these appear to be from a mypy inference issue. It maybe best to # type: ignore[list-item] just these lines and remove the ignore_errors=True from setup.cfg that applies to the whole file for all error codes.

if the mypy error is resolved in a future release, the warn_unused_ignores = True in setup.cfg means that we will be alerted and the ignores can be removed.

[WillAyd]

Thanks @simonjayhawkins