use ember-qunit@^6.2.0 on ember 3.28 scenario

Author: miguelcobain

tests/dummy/config/ember-try.js

@@ -12,7 +12,7 @@ module.exports = async function () {
           devDependencies: {
             'ember-source': '~3.28',
             '@ember/test-helpers': '^2.9.4',
-            'ember-qunit': '^7.0.0',
+            'ember-qunit': '^6.2.0',
             'ember-prism': '^0.13.0',
           },
         },