Run config/sql change action when ready for review (#7419)

Rather than running the "check-changes" action immediately when a PR is
opened, wait for the PR to be ready for review (either by being taken
out of draft mode, or by having reviewers added). This way it's possible
to create a draft PR, then create a corresponding deployment ticket
which references the PR, add that ticket to the PR description, and mark
the PR ready for review, thereby pre-empting the bot so it doesn't have
to leave a comment.

.github/workflows/issue-for-sre-handoff.yml

@@ -2,7 +2,7 @@ name: Check PR for configuration and SQL changes
 
 on:
   pull_request:
-    types: [opened, synchronize, reopened]
+    types: [ready_for_review, review_requested]
     paths:
     - 'test/config-next/*.json'
     - 'test/config-next/*.yaml'