RN: Delete guid

Summary:
Deletes `guid` because there are no more references to it in `react-native`.

Changelog:
[Internal]

Reviewed By: zackargyle

Differential Revision: D17882369

fbshipit-source-id: c3ee6d23e5fa233a7f5d2e2c7baef005384ea5b1

Libraries/vendor/core/guid.js

@@ -1,23 +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
- */
-
-/* eslint-disable no-bitwise */
-
-'use strict';
-
-/**
- * Module that provides a function for creating a unique identifier.
- * The returned value does not conform to the GUID standard, but should
- * be globally unique in the context of the browser.
- */
-function guid() {
-  return 'f' + (Math.random() * (1 << 30)).toString(16).replace('.', '');
-}
-
-module.exports = guid;

Libraries/vendor/core/guid.js.flow

@@ -1,15 +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.
- *
- * @flow strict
- * @format
- */
-
-'use strict';
-
-declare function guid(): string;
-
-module.exports = guid;