purge polyfill from firefox branch; fix 'lookup doesn't work on certain strings when certain json dictionaries are loaded' bug

mining.html

@@ -13,7 +13,6 @@ body
     font-size: 1em;
 }
 </style>
-<script src="include/browser-polyfill.min.js" charset="UTF-8"></script>
 <script src="mining.js" charset="UTF-8"></script>
 </head>