Chore upgrate ember qunit (#1376)

* Upgrade ember-qunit and ember-exam

addons/api/package.json

@@ -55,7 +55,7 @@
     "ember-load-initializers": "^2.1.2",
     "ember-maybe-import-regenerator": "^1.0.0",
     "ember-page-title": "^7.0.0",
-    "ember-qunit": "^5.1.4",
+    "ember-qunit": "^6.0.0",
     "ember-resolver": "^8.0.3",
     "ember-source": "~3.28.4",
     "ember-template-lint": "^4.14.0",