Quarantine Mattermost log in spec

Issue was raised https://gitlab.com/gitlab-org/gitlab/issues/202069

qa/qa/specs/features/browser_ui/1_manage/login/log_into_mattermost_via_gitlab_spec.rb

 # frozen_string_literal: true
 
 module QA
-  context 'Manage', :orchestrated, :mattermost do
+  context 'Manage', :orchestrated, :mattermost, quarantine: 'https://gitlab.com/gitlab-org/gitlab/issues/202069' do
     describe 'Mattermost login' do
       it 'user logs into Mattermost using GitLab OAuth' do
         Flow::Login.sign_in