DEV: upgrades from Ember 2.13 to Ember 3.5.1 (#6808)

Co-Authored-By: Bianca Nenciu <nbianca@users.noreply.github.com>
Co-Authored-By: David Taylor <david@taylorhq.com>

test/javascripts/acceptance/topic-test.js.es6

@@ -286,3 +286,10 @@ QUnit.test("select below", async assert => {
     "it should select the right number of posts"
   );
 });
+
+QUnit.test("View Hidden Replies", async assert => {
+  await visit("/t/internationalization-localization/280");
+  await click(".gap");
+
+  assert.equal(find(".gap").length, 0, "it hides gap");
+});