Fix applicable filter in idle de-labeler

What does this MR do and why?

• Makes the de-labeler act only on note events
• Fixes the label based filtering because not events don't have the labels exposed in the same fields as update events.

Expected impact & dry-runs

These are strongly recommended to assist reviewers and reduce the time to merge your change.

Action items

• N/A (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • N/A /cc @person_or_group =>
  • N/A Relevant Slack channels =>
  • N/A Engineering week-in-review