fix typo

i was sleepy lol

group_vars/matrix_servers

@@ -2743,8 +2743,8 @@ devture_postgres_managed_databases_auto: |
       'password': matrix_dendrite_database_password,
     },{
       'name': matrix_dendrite_relay_api_database,
-      'username': matrix_dendrite_relay_api_user,
-      'password': matrix_dendrite_relay_api_password,
+      'username': matrix_dendrite_database_user,
+      'password': matrix_dendrite_database_password,
     },{
       'name': matrix_dendrite_push_server_database,
       'username': matrix_dendrite_database_user,