[BE] refactor: main 브랜치 기준으로 변경 (#24)

Signed-off-by: EunJiJung <[email protected]>

Author: bianbbc87

.github/workflows/be-main.yml

@@ -1,10 +1,9 @@
 name: ECR actions for multiple folders
 
 on:
-  push:
-    # 임시 테스트 브랜치
+  pull_request:
     branches:
-      - be/setting/24-ecr
+      - main
 
 env:
   NAMESPACE_MSA: "msa"