Do not assign Composition Analysis issues for refinement

What does this MR do and why?

As discussed in gl-retrospectives/secure-sub-dept/composition-analysis#39 (comment 1649335885), we are going to iterate on our refinement process:

1. Remove the refinement bot.
2. Epic DRIs are responsible for assigning issues for refinement.
3. Engineer on support rotation is responsible for refining bugs.
4. Engineer on security rotation is responsible for refining security issues.
5. Engineering Manager is responsible for assigning feature issues for refinement.

This is step 1.

The other items are documented in Iterate on Composition Analysis refinement process (gitlab-com/content-sites/handbook!2332 - merged).

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-policies-with-a-dry-run on how to perform dry-runs for new policies.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/doc/reactive/best_practices.md#use-the-sandbox-to-test-new-processors on how to make sure a new processor can be tested.

Action items

• If adding environment variables for reactive processors, update config/triage-web.yaml and .gitlab/ci/triage-web.yml
• (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