chore(Deps): remove setimmediate (#5159)

setimmediate is a browser polyfill, and since we do not support webpack anymore, there is no reason to keep it here.

src/client/BaseClient.js

@@ -1,6 +1,5 @@
 'use strict';
 
-require('setimmediate');
 const EventEmitter = require('events');
 const RESTManager = require('../rest/RESTManager');
 const { DefaultOptions } = require('../util/Constants');