Bumped minimum grunt-contrib-qunit version to 4.0.0.

package.json

@@ -12,7 +12,7 @@
     "eslint": "^6.8.0",
     "grunt": "^1.0.1",
     "grunt-cli": "^1.2.0",
-    "grunt-contrib-qunit": "^3.1.0",
+    "grunt-contrib-qunit": "^4.0.0",
     "qunit": "^2.9.3"
   }
 }