fix: correct shell script syntax in migration job init container

chart/templates/backend-migration.job.yaml

@@ -13,16 +13,21 @@ spec:
       initContainers:
         - name: wait-for-postgres
           image: postgres:15
-          command: ['sh', '-c', 
-            'echo "Waiting for PostgreSQL to be ready..." && \
-            for i in $(seq 1 30); do \
-              if pg_isready -h postgres-service -p 5432 -U prod_admin; then \
-                echo "PostgreSQL is ready!" && exit 0; \
-              fi; \
-              echo "Attempt $i: PostgreSQL is not ready yet. Waiting..." && \
-              sleep 10; \
-            done; \
-            echo "PostgreSQL failed to become ready in time" && exit 1;']
+          command: 
+            - /bin/sh
+            - -c
+            - |
+              echo "Waiting for PostgreSQL to be ready..."
+              for i in $(seq 1 30); do
+                if pg_isready -h postgres-service -p 5432 -U prod_admin; then
+                  echo "PostgreSQL is ready!"
+                  exit 0
+                fi
+                echo "Attempt $i: PostgreSQL is not ready yet. Waiting..."
+                sleep 10
+              done
+              echo "PostgreSQL failed to become ready in time"
+              exit 1
           env:
             - name: PGPASSWORD
               value: "{{ .Values.backend.env.POSTGRES_PASSWORD }}"