ci(labeler): stop cancelling the in-flight run, which kept Renovate from automerging (#7279)

.github/workflows/pull-request-target.yml

@@ -5,9 +5,10 @@ on:
 # Do not execute arbitrary code on this workflow.
 # See warnings at https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#pull_request_target
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
-  cancel-in-progress: true
+# No concurrency group. Renovate labels its PR right after opening it, so a cancelling group left a cancelled
+# `labeler` check run on the head commit, and Renovate reads any cancelled check run as a pending branch it never
+# automerges. A non-cancelling group still cancels a queued run when a third event arrives. The job is idempotent
+# and seconds on ubuntu-slim, so every run can simply finish.
 
 jobs:
   labeler: