Github Actions pull_request synchronize runs on PR open anyway (matrix-org#2418)

Author: t3chguy

.github/workflows/pull_request.yaml

@@ -1,7 +1,7 @@
 name: Pull Request
 on:
   pull_request_target:
-    types: [ opened, edited, labeled, unlabeled, synchronize ]
+    types: [ edited, labeled, unlabeled, synchronize ]
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.head.ref }}
   cancel-in-progress: true