test: exclude playground from coverage

[Barbapapazes]

Hello 👋,

This PR add the flag coverage.exclude to the test coverage command to avoid to include the playground folder in the coverage report.

This PR also remove the playground coverage in the CI.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Please upload report for BASE (main@53cd585). Learn more about missing BASE report.

Additional details and impacted files

@@          Coverage Diff           @@
##             main    #159   +/-   ##
======================================
  Coverage        ?   6.73%           
======================================
  Files           ?       7           
  Lines           ?     609           
  Branches        ?      20           
======================================
  Hits            ?      41           
  Misses          ?     562           
  Partials        ?       6           

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[pi0]

Thanks, added in eb5c799af587ebfd6049fabc6fe1caec30cd256f