Fix detection of processor location in Triage::Reaction

What does this MR do and why?

This fixes an issue after !1477 (merged) was merged, where the path to processors doesn't include triage-ops when run inside the production container.

Instead the path is in the form /srv/rack/triage/processor/community/automated_review_request_doc.rb, so we changed the detection logic to be agnostic and actually match a path we know exists in all cases (i.e. triage/processor).

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