Make PR notification less noisy (#176)

.github/workflows/pr_notification.yml

@@ -2,7 +2,7 @@ name: GSI Chatroom PR Notification
 
 on:
   pull_request:
-    types: [assigned, opened, ready_for_review, reopened, review_requested]
+    types: [review_requested]
 
 jobs:
   notify-pull-request: