Adjust Danger logic for stable branches

What does this MR do and why?

Backport of !128409 (merged) so we can have the updated Danger rule take effect in the 16-0-stable-ee branch. I intend to backport to all branches in the next security release since they will be the most targeted branches for backports.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The original MR has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:package-and-test-ee job has either succeeded or been approved by a Software Engineer in Test.

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