chore(ci): remove synchronize trigger for label-schema (#12823)

.github/workflows/label-schema.yml

@@ -1,7 +1,7 @@
 name: Pull Request Schema Labeler
 on:
   pull_request:
-    types: [opened, edited, synchronize, labeled, unlabeled]
+    types: [opened, edited, labeled, unlabeled]
 jobs:
   schema-change-labels:
     if: "${{ contains(github.event.*.labels.*.name, 'schema-change-noteworthy') }}"