Unquarantine end-to-end test for ee feature

Potentially closes:
https://gitlab.com/gitlab-org/quality/staging/issues/58

qa/qa/specs/features/browser_ui/2_plan/ee_epic/promote_issue_to_epic_spec.rb

 # frozen_string_literal: true
 
 module QA
-  # https://gitlab.com/gitlab-org/quality/staging/issues/58
-  context 'Plan', :quarantine do
+  context 'Plan' do
     describe 'promote issue to epic' do
       let(:issue_title) { "My Awesome Issue #{SecureRandom.hex(8)}" }
 
@@ -24,7 +23,15 @@ module QA
         end
 
         Page::Project::Issue::Show.perform do |show|
-          show.comment('/promote')
+          # Due to the randomness of tests execution, sometimes a previous test
+          # may have changed the filter, which makes the below action needed.
+          # TODO: Make this test completely independent, not requiring the below step.
+          show.select_all_activities_filter
+          # We add a space together with the '/promote' string to avoid test flakiness
+          # due to the tooltip '/promote Promote issue to an epic (may expose
+          # confidential information)' from being shown, which may cause the click not
+          # to work properly.
+          show.comment('/promote ')
 
           expect(show).to have_content("promoted to epic")
         end