ci: use more workers to speed up tests in pipeline

[bearomorphism]

From 3 workers to auto workers.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.92%. Comparing base (6990d51) to head (ca09a97).
⚠️ Report is 5 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1751   +/-   ##
=======================================
  Coverage   97.92%   97.92%           
=======================================
  Files          60       60           
  Lines        2604     2604           
=======================================
  Hits         2550     2550           
  Misses         54       54           

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[noirbizarre]

Let's wait for #1752 to be merged to master build is fixed, then LGTM 🚀 (let's benefit from all those cores we have now).