[RN] Drop no longer needed polyfills

They were required only on Android because of its old JSC version. With the JSC
version bump they are no longer required.

index.android.js

@@ -1,26 +1,2 @@
-// The type field of react-native application loader's React Element is created
-// as number and not Symbol, because it's not been defined by the polyfill yet.
-// We import the application renderer, before Symbol is defined, in order to use
-// number types as well. Otherwise this will result in the invariant exception,
-// because fiber thingy will not recognise root react-native component as React
-// Element, but as an Object.
-//
-// See node_modules/react-native/Libraries/polyfills/babelHelpers.js
-// :babelHelpers.createRawReactElement - that's where first react-native element
-// is created (super early - it's the app loader).
-//
-// See node_modules/react-native/Libraries/Renderer/ReactNativeFiber-dev.js
-// and look for REACT_ELEMENT_TYPE definition - it's defined later when Symbol
-// has been defined and type will not match.
-//
-// As an alternative solution we could stop using/polyfilling Symbols and
-// replace with classpath string constants or some kind of a wrapper around
-// that.
-
-import 'react-native/Libraries/ReactNative/renderApplication';
-
-// Android doesn't provide Symbol
-import 'es6-symbol/implement';
-
 import './react/index.native';
 

package.json

@@ -36,8 +36,6 @@
     "@atlaskit/tooltip": "9.1.1",
     "@webcomponents/url": "0.7.1",
     "autosize": "1.18.13",
-    "es6-iterator": "2.0.3",
-    "es6-symbol": "3.1.1",
     "i18next": "8.4.3",
     "i18next-browser-languagedetector": "2.0.0",
     "i18next-xhr-backend": "1.4.2",

react/features/base/lib-jitsi-meet/native/polyfills-browser.js

@@ -1,4 +1,3 @@
-import Iterator from 'es6-iterator';
 import BackgroundTimer from 'react-native-background-timer';
 import '@webcomponents/url'; // Polyfill for URL constructor
 
@@ -123,18 +122,6 @@ function _visitNode(node, callback) {
         global.removeEventListener = () => {};
     }
 
-    // Array.prototype[@@iterator]
-    //
-    // Required by:
-    // - for...of statement use(s) in lib-jitsi-meet
-    const arrayPrototype = Array.prototype;
-
-    if (typeof arrayPrototype['@@iterator'] === 'undefined') {
-        arrayPrototype['@@iterator'] = function() {
-            return new Iterator(this);
-        };
-    }
-
     // document
     //
     // Required by: