Move unused sleep module out of repo

Reviewed By: rafeca

Differential Revision: D6566682

fbshipit-source-id: 48cff465ace25d6d38b8574006e0c54081b8fbde

packages/metro/src/lib/sleep.js

@@ -1,21 +0,0 @@
-/**
- * Copyright (c) 2015-present, Facebook, Inc.
- * All rights reserved.
- *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
- *
- * @flow
- * @format
- */
-
-'use strict';
-
-function sleep(duration: number): Promise<void> {
-  return new Promise(resolve => {
-    setTimeout(resolve, duration);
-  });
-}
-
-module.exports = sleep;