message: docs: document the `PR action: rerun CI at HEAD` label in `TRIAGE_AND_LABELS.md`
  Related to
  PR Close
diff: @@ -202,3 +202,9 @@ There should always be a comment added to the PR to explain why the caretaker's
  The comment should be formatted like this: `merge-assistance: <explain what kind of assistance you need, and if not obvious why>`
  For example, the PR owner might not be a Googler and needs help to run g3sync; or one of the checks is failing due to external causes and the PR should still be merged.
  +
  +### `PR action: rerun CI at HEAD`
  +* _**Who adds it:** Any team member._
  +* _**Who removes it:** The Angular Bot, once it triggers the CI rerun._
  +
  +This label can be added to instruct the Angular Bot to rerun the CI jobs for the PR at latest HEAD of the branch it targets.
  