AtlassianBannerRemove.user.js

// ==UserScript==
// @name testName
// @namespace anonDeveloper
// @description This script will automagically blah blah blah
// @include *
// @match https://*/jira/browse
// ==/UserScript==

// See private file for otheradditions

if (window.location.href.match('.*jira/browse/.*')) {
     setTimeout(function() {
          if (document.getElementById('announcement-banner') != null) {
            document.getElementById('announcement-banner').remove()
          }
     }, 2000);
}