[20486] Avoid running GitHub CI if PR has conflicts (backport #4489)

[mergify]

This is an automatic backport of pull request #4489 done by Mergify.
Cherry-pick of 3ed793c has failed:

On branch mergify/bp/2.13.x/pr-4489
Your branch is up to date with 'origin/2.13.x'.

You are currently cherry-picking commit 3ed793cc3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .github/workflows/mac-ci.yml
	modified:   .github/workflows/sanitizer-tests.yaml
	modified:   .github/workflows/thread-sanitizer.yaml
	modified:   .github/workflows/windows-ci.yml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/documentation-tests.yaml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[mergify]

Cherry-pick of 3ed793c has failed:

On branch mergify/bp/2.13.x/pr-4489
Your branch is up to date with 'origin/2.13.x'.

You are currently cherry-picking commit 3ed793cc3.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .github/workflows/mac-ci.yml
	modified:   .github/workflows/sanitizer-tests.yaml
	modified:   .github/workflows/thread-sanitizer.yaml
	modified:   .github/workflows/windows-ci.yml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/workflows/documentation-tests.yaml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[JesusPoderoso]

@richiprosima please test this