[FIX] gradlew 경로 수정

Author: ohksj77

.github/workflows/backend-cd.yml

@@ -39,7 +39,7 @@ jobs:
           echo "TMAP_URL=${{ secrets.TMAP_URL }}" >> $GITHUB_ENV
 
       - name: Grant execute permission for gradlew
-        run: chmod +x gradlew
+        run: chmod +x ./backend/gradlew
         shell: bash
 
       - name: Build with jib