Update integration-tests.test.yml

Oops.  SUT System under test is a service not a top level object.

postgres-backup-s3/integration-tests.test.yml

@@ -12,11 +12,11 @@ services:
       - source: master-db-config_2
         target: /etc/postgresql/postgresql.conf
     command: -c 'config_file=/etc/postgresql/postgresql.conf'
-configs:
-  master-db-config:
-    file: ./config/master.conf
   sut:
     build: .
     command: 'sh integration-tests.sh'
     depends_on:
       - postgres
+configs:
+  master-db-config:
+    file: ./config/master.conf