github: fix needs-more-info label race condition

Remove the `issues: labeled` trigger from the timer workflow.

When both workflows triggered on label addition, the comment workflow
would post the bot comment, and by the time the timer workflow ran,
issue-manager would see "a comment was added after the label" and
immediately remove the label due to `remove_label_on_comment: true`.

The timer workflow now only runs on:
- Daily cron (to close stale issues)
- issue_comment (to remove label when humans respond)
- workflow_dispatch (for manual testing)

.github/workflows/needs-more-info-timer.yml

@@ -5,8 +5,6 @@ on:
     - cron: "0 0 * * *" # Daily at midnight UTC
   issue_comment:
     types: [created]
-  issues:
-    types: [labeled]
   workflow_dispatch:
 
 jobs: