Fix link to label command docs in thanks message

What does this MR do and why?

This fixes the link to the label command for the thanks message to point to the direct section, where the title was updated in Add docs for reactive unlabel command (gitlab-com/www-gitlab-com!125054 - merged) resulting in the inaccurate link.

Expected impact & dry-runs

None.

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