[fix] hotfix workflow 수정

.github/workflows/hotfix.yml

@@ -7,7 +7,8 @@ on:
 
 jobs:
   hotfix:
-    if: github.event.pull_request.merged == false
+    # commit message가 [hotfix]로 시작하면 실행
+    if: startsWith(github.event.head_commit.message, '[hotfix]')
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code