Update FetchRequest.js

Author: songyumeng

src/common/util/FetchRequest.js

@@ -1,8 +1,8 @@
 /* Copyright© 2000 - 2019 SuperMap Software Co.Ltd. All rights reserved.
  * This program are made available under the terms of the Apache License, Version 2.0
  * which accompanies this distribution and is available at http://www.apache.org/licenses/LICENSE-2.0.html.*/
-import "./PromisePolyfill"
-import 'fetch-ie8'
+import 'promise-polyfill/dist/polyfill';
+import 'fetch-ie8';
 import fetchJsonp from 'fetch-jsonp';
 import {
     SuperMap
@@ -427,4 +427,4 @@ SuperMap.Util.RequestJSONPPromise = {
         });
         return me.issue(config);
     }
-};
+};