Upgrade ember-qunit, because @ember/test-helpers requires it

Author: NullVoxPopuli

docs/package.json

@@ -52,7 +52,7 @@
     "ember-load-initializers": "^2.1.2",
     "ember-maybe-import-regenerator": "^1.0.0",
     "ember-page-title": "8.1.0",
-    "ember-qunit": "^5.1.5",
+    "ember-qunit": "^8.0.2",
     "ember-resolver": "^11.0.1",
     "ember-source": "~3.28.3",
     "ember-source-channel-url": "^3.0.0",