updated engine version for db

cloudformation/stack.yaml

@@ -3682,7 +3682,7 @@ Resources:
       DBSubnetGroupName: !Ref AppDbSubnet
       Engine: aurora-postgresql
       EngineMode: serverless
-      EngineVersion: 12
+      EngineVersion: 11.13
       KmsKeyId: !If [CreateDiskEncryptionKey, !Ref DiskKmsKey, !Ref "AWS::NoValue"]
       StorageEncrypted: true
       MasterUsername: !If [IsRestore, !Ref "AWS::NoValue", !Join ['', ['{{resolve:secretsmanager:', !Ref AppDbSecret, ':SecretString:username}}' ]]]