chore: update codecov/codecov-action action to v4

[federicobond]

See https://cloud-native.slack.com/archives/C0344AANLA1/p1712852328361719

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.35%. Comparing base (faf02a9) to head (21c2f3a).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #317      +/-   ##
==========================================
+ Coverage   97.10%   97.35%   +0.24%     
==========================================
  Files          27       27              
  Lines        1176     1211      +35     
==========================================
+ Hits         1142     1179      +37     
+ Misses         34       32       -2     

Flag	Coverage Δ
unittests	97.35% <ø> (+0.24%)	⬆️

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