Fix permissions for ready command

What does this MR do and why?

The @gitlab-bot request_review command can currently be executed by every community member.

Example here: gitlab-org/gitlab!89746 (comment 986790048) (I'm the author of the MR, but Lee was able to successfully execute the command).

Expected impact & dry-runs

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

See https://gitlab.com/gitlab-org/quality/triage-ops/-/tree/master/doc/scheduled#testing-with-a-dry-run on how to perform dry-runs.

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