ci: add concurrency group and remove bot filter in pr-review-trigger

Add a concurrency group keyed on PR number to prevent duplicate reviews
from simultaneous review_requested events.

Remove the sender.type != 'Bot' guard so Dependabot PRs remain
reviewable — per maintainer feedback, those reviews are useful for
catching behavior changes in dependency updates.

Signed-off-by: Derek Misler <derek.misler@docker.com>

.github/workflows/pr-review-trigger.yml

@@ -7,8 +7,17 @@ on:
 
 permissions: {}
 
+# Deduplicate simultaneous pull_request events for the same fork PR.
+# When reviewers are requested at the same time, GitHub fires multiple
+# review_requested events. Without this group each event triggers a
+# separate review via workflow_run, producing duplicate reviews.
+concurrency:
+  group: pr-review-trigger-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
 jobs:
   save-context:
+    if: github.event.pull_request.head.repo.fork
     runs-on: ubuntu-latest
     steps:
       - name: Save event context