Fix admin area selector in GitLab QA

Fixes gitlab-org/gitlab-qa#66

qa/qa/page/main/menu.rb

@@ -11,7 +11,7 @@ module QA
         end
         def go_to_admin_area
-          within_top_menu { click_link 'Admin area' }
+          within_top_menu { find('.admin-icon').click }
         end
         def sign_out