Fix newsfragment check being cancelled on rapid PR events (#64447)

Change cancel-in-progress from true to false so that concurrent
runs queue instead of cancelling each other. This check is very
lightweight (single API call) so queueing has no downside, and
avoids spurious "Cancelled" status on PRs that receive multiple
events in quick succession (e.g. push + label change).

Author: potiuk

.github/workflows/check-newsfragment-pr-number.yml

@@ -32,7 +32,7 @@ permissions:
 
 concurrency:
   group: check-newsfragment-${{ github.event.pull_request.number }}
-  cancel-in-progress: true
+  cancel-in-progress: false
 
 jobs:
   check-newsfragment-pr-number: