Fix CI for Python 3.6

[kwabenantim]

Description

• This PR supports Fix CI for Python 3.6 #265
• It updates the CI workflow to use the latest version of the setup-python action which can fetch Python versions that don't come pre-installed on github runners (setup-actions changelog).

Motivation and Context

• Tests failed for PR Bump urllib3 from 1.26.5 to 1.26.17 in /dev-requirements #264 because Python 3.6 had been removed from github runners.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Documentation checklist

• I have updated all documentation in the code where necessary.
• I have checked spelling in all (new) comments and documentation.
• I have added a note to RELEASE.md if relevant (new feature, breaking change, or notable bug fix).
• I have updated version & citation.txt & citation.cff version.

Testing

• Testing is done automatically and codecov shows test coverage
• This cannot be tested automatically

[codecov]

Codecov Report

Merging #266 (927c6d9) into master (5551e73) will not change coverage.
Report is 7 commits behind head on master.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #266   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           30        30           
  Lines         1791      1791           
=========================================
  Hits          1791      1791           

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