Fix community MRs report schedule to be weekly

What does this MR do and why?

This is a follow-up of !1335 (merged) where the community MRs report was inadvertently changed to be bi-weekly.

This changes it back to be weekly.

Expected impact & dry-runs

I was surprised to not see a report this week (last one was triage-reports#7462 (closed)).

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