portablectl: actually allow set-limit with one arg

In the man page and in the actual code, the first arg is
optional. But the arg limit in the verbs table did not allow
only one arg to be specified.

Fixes: 61d0578b07

src/portable/portablectl.c

@@ -1215,7 +1215,7 @@ static int verb_remove_image(int argc, char *argv[], uintptr_t _data, void *user
         return 0;
 }
 
-VERB(verb_set_limit, "set-limit", "[NAME|PATH] LIMIT", 3, 3, 0,
+VERB(verb_set_limit, "set-limit", "[NAME|PATH] LIMIT", 2, 3, 0,
      "Set image or pool size limit (disk quota)");
 static int verb_set_limit(int argc, char *argv[], uintptr_t _data, void *userdata) {
         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;