Remove support for Python 3.9

[GlassOfWhiskey]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 75.67568% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.13%. Comparing base (89b7c09) to head (c2e2099).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cwltest/compare.py	85.18%	3 Missing and 1 partial ⚠️
cwltest/main.py	0.00%	2 Missing ⚠️
cwltest/hooks.py	0.00%	1 Missing ⚠️
cwltest/plugin.py	50.00%	1 Missing ⚠️
cwltest/utils.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #258      +/-   ##
==========================================
+ Coverage   45.05%   45.13%   +0.07%     
==========================================
  Files           9        9              
  Lines         850      853       +3     
  Branches      173      172       -1     
==========================================
+ Hits          383      385       +2     
- Misses        428      429       +1     
  Partials       39       39              

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[mr-c]

@GlassOfWhiskey Thank you! I presume you don't need a new cwltest release anytime soon?