Revert "GH: Allow backport workflow to trigger actions"

[tvdeyen]

Reverts #6164

From my comment on #6179

This does not help. It only triggers the workflow when a user with workflow permissions create the PR (me in this case). But it does not work if another action creates a PR with the default GITHUB_TOKEN github creates.

See sorenlouv/backport-github-action#79 for background

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.64%. Comparing base (2d70d96) to head (b65baaf).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6180      +/-   ##
==========================================
- Coverage   88.81%   86.64%   -2.17%     
==========================================
  Files         835      514     -321     
  Lines       18158    11894    -6264     
==========================================
- Hits        16127    10306    -5821     
+ Misses       2031     1588     -443     

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