Updated classifiers in setup.py

[rickecon]

This PR updates the classifiers in setup.py. This is important because the previous classifier of 'License :: OSI Approved :: CC0 1.0 Universal public domain dedication' was not valid and was breaking our publish_to_pypi.yml GitHub Action.

ERROR    HTTPError: 400 Bad Request from https://upload.pypi.org/legacy/        
         Invalid value for classifiers. Error: Classifier 'License :: OSI       
         Approved :: CC0 1.0 Universal public domain dedication' is not a valid 
         classifier. 

This change should fix the issue. But the only way to test whether it works is to merge the PR.

@jdebacker. Will you please merge this PR as soon as all the tests (or 4 of the 6 tests) pass? Thanks.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6e42207) 73.76% compared to head (8200d1f) 73.76%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #75   +/-   ##
=======================================
  Coverage   73.76%   73.76%           
=======================================
  Files          24       24           
  Lines        1616     1616           
=======================================
  Hits         1192     1192           
  Misses        424      424           

Flag	Coverage Δ
unittests	73.76% <ø> (ø)

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Files	Coverage Δ
setup.py	0.00% <ø> (ø)

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[rickecon]

@jdebacker. I think this PR is ready. The last two tests (Windows, Python 3.9 and 3.10) are just stalled at the test stage.