Optimize the CI milestone reminder (#39196)

This PR narrows down the matching pattern for the milestone reminder to
only the descriptions that explicitly contain one of the closing keywords
followed by the issue (number).

To verify that the proposed solution works, please check:
- https://regexr.com/7sk94

Also see the list of the closing keywords as defined by GitHub.
https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/using-keywords-in-issues-and-pull-requests



* Make the pattern case insensitive

Co-authored-by: Nicolò Pretto <info@npretto.com>

.github/workflows/check-milestone.yml

@@ -26,8 +26,8 @@ jobs:
 
             // the github API doesn't expose linked issues, so we have to parse the body ourselves
             function getLinkedIssueId(pull) {
-              // https://regexr.com/7mjnp
-              const match = pull.data.body.match(/(\/issues\/|#)(\d+)/);
+              // https://regexr.com/7sk94
+              const match = pull.data.body.match(/(close(s|d)?|fixe?(s|d)?|resolve(s|d)?) (#|https?:\/\/github.com\/.+\/issues\/)(\d+)/i);
               return match && match?.[2];
             }