fix(ci): failure alerts are not triggered on ROSA schedule integration

[leiicamundi]

Which problem does the PR fix?

• Alerts are not triggered
• When performing test upgrade on main, the fetch command fails due to the current already on main (this error wasn't triggered before due to the fact that integration tests were always launched from PRs).
  See
  https://github.com/camunda/camunda-platform-helm/actions/runs/9802466140/job/27068549929

What's in this PR?

This fix implements the same logic as we have in
https://github.com/camunda/camunda-tf-eks-module/blob/85f9a6913e3a14c0c0ce966e9dc434762e1448b2/.github/workflows/tests.yml#L184

Checklist

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• In-repo documentation are updated (if needed).

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• Did all checks/tests pass in the PR?

[aabouzaid]

LGTM, thank you 👍