MAINT: Fix version specifier

[larsoner]

Should fix failures seen like https://github.com/pyvista/pyvistaqt/actions/runs/4041478088/jobs/6948090794

      error in pyvistaqt setup command: 'python_requires' must be a string containing valid version specifiers; Invalid specifier: '>=3.7.*'

[codecov]

Codecov Report

Merging #296 (ec6efbb) into main (03ff77f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #296   +/-   ##
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  Coverage   97.31%   97.31%           
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  Files           8        8           
  Lines         670      670           
  Branches       82       82           
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  Hits          652      652           
  Partials       18       18           

[larsoner]

This test has been spuriously failing:

_____________ ERROR at teardown of test_background_plotting_orbit ______________
tests/conftest.py:97: in check_gc
    assert len(after) == 0, msg
E   AssertionError: Not all objects GCed:
E     vtkWeakReference: []
E     vtkFloatArray: []

rather than restarting CIs now and in the future, I added a @pytest.mark.allow_bad_gc_pyside and a comment about it

[tkoyama010]

Thanks @larsoner