nspawn: fix barrier-destroy call

I dropped the cleanup-helper before pushing so use _cleanup_() directly.

src/nspawn/nspawn.c

@@ -3073,7 +3073,7 @@ int main(int argc, char *argv[]) {
 
         for (;;) {
                 ContainerStatus container_status;
-                _barrier_destroy_ Barrier barrier = { };
+                _cleanup_(barrier_destroy) Barrier barrier = { };
                 struct sigaction sa = {
                         .sa_handler = nop_handler,
                         .sa_flags = SA_NOCLDSTOP,