docs: fix setTimeout example

Based on #11447 (comment)

Author: posva

website/versioned_docs/version-27.2/TimerMocks.md

@@ -25,6 +25,7 @@ module.exports = timerGame;
 'use strict';
 
 jest.useFakeTimers();
+jest.spyOn(global, 'setTimeout');
 
 test('waits 1 second before ending the game', () => {
   const timerGame = require('../timerGame');