fix: add a delay before the contributors workflow sets auto-merge

[fredbi]

Problem: when auto-merge is set, the PR merges as soon as the required check status is okay, meaning that the next job that uploads test coverage always fails (branch is deleted). This is not blocking but kind of untidy.

Solution: introduced a loop that waits for all PR jobs to complete before auto-merge is enabled.

Change type

Please select: 🆕 New feature or enhancement|🔧 Bug fix'|📃 Documentation update

Short description

Fixes

Full description

Checklist

• I have signed all my commits with my name and email (see DCO. This does not require a PGP-signed commit
• I have rebased and squashed my work, so only one commit remains
• I have added tests to cover my changes.
• I have properly enriched go doc comments in code.
• I have properly documented any breaking change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (56a1aea) to head (fa2b0fb).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #37   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines            8         8           
=========================================
  Hits             8         8           

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