Remove `React.js` from RN open source

Summary: This diff removes the `React.js` forwarding module from RN open source which was only used for haste requires. I moved this file to FB internal and manually changed requires from `React` to `react`. However, I can't fully remove this forwarding module because we have files shared from www that expect to require React via the capitalized named.

Reviewed By: yungsters

Differential Revision: D15738887

fbshipit-source-id: b5b6c0be258582cfad92c13d174e5490c75152d9

Libraries/react-native/React.js

@@ -1,12 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @format
- */
-
-'use strict';
-
-module.exports = require('react');