chore(backport release-0.8): fix(promotion): wait for open pull request

[akuitybot]

Automated backport to release-0.8, triggered by a label in #2451.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 46.72%. Comparing base (5b6cfa0) to head (8bde16c).
Report is 1 commits behind head on release-0.8.

Files	Patch %	Lines
internal/controller/promotion/pullrequest.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-0.8    #2452      +/-   ##
===============================================
- Coverage        46.72%   46.72%   -0.01%     
===============================================
  Files              246      246              
  Lines            17745    17747       +2     
===============================================
  Hits              8292     8292              
- Misses            9023     9025       +2     
  Partials           430      430              

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