chore: update emoji in no new post alert

Author: injoonH

apps/kaist/portal/worker.py

@@ -133,7 +133,7 @@ def _send_success_single_alert(post_id: int) -> None:
 
     @staticmethod
     def _send_no_new_post_alert() -> None:
-        slack_webhook_client.send(text=f":blobhaj_ghostie_alive: 새로운 공지가 없어요.")
+        slack_webhook_client.send(text=f":blobhaj_innocent: 새로운 공지가 없어요.")
         log.info("KAIST Portal Crawler :: No new post found")
 
     @staticmethod