Unquarantine epics management E2E spec

https://gitlab.com/gitlab-org/gitlab/-/issues/334767Signed-off-by: Nailia Iskhakova <niskhakova@gitlab.com>

qa/qa/specs/features/ee/browser_ui/2_plan/epic/epics_management_spec.rb

 # frozen_string_literal: true
 
 module QA
-  RSpec.describe 'Plan', :reliable, quarantine: { issue: 'https://gitlab.com/gitlab-org/gitlab/-/issues/334767', type: :investigating } do
+  RSpec.describe 'Plan', :reliable do
     describe 'Epics Management' do
       before do
         Flow::Login.sign_in