Build: Update grunt-contrib-qunit

This also switches us to the new Chrome Headless mode.

Ref https://developer.chrome.com/articles/new-headless/
Ref https://pptr.dev/#default-runtime-settings

package.json

@@ -59,7 +59,7 @@
 		"grunt-compare-size": "0.4.2",
 		"grunt-contrib-concat": "2.1.0",
 		"grunt-contrib-csslint": "2.0.0",
-		"grunt-contrib-qunit": "7.0.0",
+		"grunt-contrib-qunit": "8.0.1",
 		"grunt-contrib-requirejs": "1.0.0",
 		"grunt-contrib-uglify": "5.2.2",
 		"grunt-eslint": "24.0.1",