Add idle community mrs policy to schedule

What does this MR do and why?

Describe in detail what your merge request does and why.

Adds the stale idle Community contribution policy to the gitlab-org hygiene schedule so that the Community report for Contributor success can use the new labelling policies.

From https://gitlab.slack.com/archives/CMA7DQJRX/p1646042740661109

Expected impact & dry-runs

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

Action items

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