One sleep to rule them all. Zzz

Summary: Boyscouted some code duplication away.

Reviewed By: jknoxville

Differential Revision: D29731016

fbshipit-source-id: d5f1677a667f032f6e7e031da296be26e1976932

desktop/plugins/public/shared_preferences/src/__test__/shared_preferences.spec.tsx

@@ -7,13 +7,9 @@
  * @format
  */
 
-import {TestUtils} from 'flipper-plugin';
+import {TestUtils, sleep} from 'flipper-plugin';
 import * as plugin from '..';
 
-async function sleep(ms: number) {
-  return new Promise<void>((resolve) => setTimeout(() => resolve(), ms));
-}
-
 // this testing is inspired by Flipper sample app
 test('general plugin logic testing', async () => {
   const {instance, onSend, connect, sendEvent} = TestUtils.startPlugin(plugin, {