Rename from MWPS to auto-merge

What does this MR do and why?

Edits text used in the "did you forget to run a pipeline?" comment to take out the "merge when pipeline succeeds" language in favor of "auto-merge," which is what the button says now.

Related issues

• Related to Plan for changes from 'auto_merge_labels_mr_wid... (gitlab-org/technical-writing#782)
• Related to Replace merge strategy labels with `Auto-merge`... (gitlab-org/gitlab#359057 - closed)

Expected impact & dry-runs

The text of the comment should change.

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