Bump action version and update cached Matplotlib

[YigitElma]

1. Bumps the Wandalen/wretry.action version to the latest to solve the Node.js version warning as mentioned in Bump Github action versions to avoid js node 16 deprecation warning #843
2. For regression/unit tests, we use specific matplotlib version, but we don't cache that version. If we instead cache that we can save time.
3. Bumpscodecov version to v4

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.44%. Comparing base (75eafcc) to head (5376e88).
Report is 2219 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1257      +/-   ##
==========================================
- Coverage   95.45%   95.44%   -0.01%     
==========================================
  Files          95       95              
  Lines       23423    23423              
==========================================
- Hits        22358    22356       -2     
- Misses       1065     1067       +2     

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