CI: Remove label event types from PR pull workflow

This fix was also applied on obs-studio, as creating a labeled pull
request would trigger this workflow twice otherwise.

.github/workflows/pr-pull.yaml

@@ -6,7 +6,7 @@ on:
     paths-ignore:
       - '**.md'
     branches: [master, main]
-    types: [ opened, synchronize, reopened, labeled, unlabeled ]
+    types: [ opened, synchronize, reopened ]
 permissions:
   contents: read
 concurrency: