systemctl: fix indentation of cgroup tree

Follow-up for 0d588deae2.

In that commit the output got moved a 2 chars to the right, hence make
sure to also shift the cgroup tree to the right, so that it gets
properly aligned under the cgroup path again.

src/systemctl/systemctl.c

@@ -4576,7 +4576,7 @@ static void print_status_info(
 
         if (i->control_group) {
                 _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
-                static const char prefix[] = "           ";
+                static const char prefix[] = "             ";
                 unsigned c;
 
                 printf("     CGroup: %s\n", i->control_group);