ci: remove main/master sync

[moe-ad]

The migration master to main migration period was end of September.
TO-DO: make the master branch read-only by locking it @PProfizi.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.16%. Comparing base (d68421e) to head (80cacf1).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #919   +/-   ##
=======================================
  Coverage   85.16%   85.16%           
=======================================
  Files          52       52           
  Lines        5217     5217           
=======================================
  Hits         4443     4443           
  Misses        774      774           

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