Remove global babelHelpers and regenerator (#21283)

Summary:
Follow up to facebook/metro@8932a9c

Babel helpers and regenerator runtime will be imported automatically from `babel/runtime`. We still need to add the global regeneratorRuntime for jest tests since we disable babel-runtime currently.
Pull Request resolved: facebook/react-native#21283

Reviewed By: mjesun

Differential Revision: D10010963

Pulled By: rafeca

fbshipit-source-id: da5e23dd901f8f8940d46816b4fc9290d0e28c76

IntegrationTests/RCTRootViewIntegrationTestApp.js

@@ -10,8 +10,6 @@
  */
 'use strict';
 
-require('regenerator-runtime/runtime');
-
 var React = require('React');
 var ReactNative = require('react-native');
 

jest/setup.js

@@ -108,7 +108,6 @@ jest
   })
   .mock('ensureComponentIsNative', () => () => true);
 
-const mockEmptyObject = {};
 const mockNativeModules = {
   AlertManager: {
     alertWithArgs: jest.fn(),

package.json

@@ -147,6 +147,7 @@
     "react": "16.6.3"
   },
   "dependencies": {
+    "@babel/runtime": "^7.0.0",
     "absolute-path": "^0.0.0",
     "art": "^0.10.0",
     "babel-core": "^6.24.1",

rn-get-polyfills.js

@@ -19,5 +19,4 @@ module.exports = () => [
   require.resolve('./Libraries/polyfills/Array.prototype.es6.js'),
   require.resolve('./Libraries/polyfills/Array.es6.js'),
   require.resolve('./Libraries/polyfills/Object.es7.js'),
-  require.resolve('./Libraries/polyfills/babelHelpers.js'),
 ];