Firefox Greasemonkey Github Remove Dark Headder and Bring Back Light Header

user.github.js

// ==UserScript==
// @name        github
// @namespace   YOURNAMESPACEHERE
// @description modify github bring back light header
// @include     https://github.com/*
// @include     https://gist.github.com/*
// @version     1
// @grant       none
// @require https://code.jquery.com/jquery-1.12.4.min.js
// ==/UserScript==
// get Greasmonkey at https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/
$('.header-dark').each(function(index, element){
  $(element).removeClass('header-dark');
  $(element).addClass('header-light')
});