DEV: fix the mobile spec (#621)

In discourse/discourse#30242, the topic footer buttons mobile dropdown can be replaced by the button if there's only one option.

This fixes the spec that was clicking on the dropdown button before checking there was no assign option.

test/javascripts/acceptance/assign-disabled-test.js

@@ -1,4 +1,4 @@
-import { click, visit } from "@ember/test-helpers";
+import { visit } from "@ember/test-helpers";
 import { test } from "qunit";
 import { acceptance } from "discourse/tests/helpers/qunit-helpers";
 
@@ -9,7 +9,6 @@ acceptance("Discourse Assign | Assign disabled mobile", function (needs) {
 
   test("Footer dropdown does not contain button", async function (assert) {
     await visit("/t/internationalization-localization/280");
-    await click(".topic-footer-mobile-dropdown-trigger");
     assert.dom(".assign").doesNotExist();
   });
 });