nspawn: fix settings leak for init parameter

Fixes https://github.com/systemd/systemd/issues/33960

Follow-up for ce2291730d

src/nspawn/nspawn-settings.c

@@ -122,6 +122,7 @@ Settings* settings_free(Settings *s) {
         if (!s)
                 return NULL;
 
+        free(s->init);
         strv_free(s->parameters);
         strv_free(s->environment);
         free(s->user);