Build: remove now-unneeded phantomjs-polyfill dependency

Author: dmethvin

package-lock.json

@@ -41,7 +41,6 @@
     "grunt-qunit-istanbul": "1.0.0",
     "jquery": "3.1.1",
     "load-grunt-tasks": "3.5.2",
-    "phantomjs-polyfill": "0.0.2",
     "qunitjs": "2.0.1",
     "testswarm": "1.1.0"
   },