Remove unneeded stub

These specs don't really need it and this was causing a broken spec
in https://gitlab.com/gitlab-org/gitlab/-/issues/327668

ee/spec/features/epics/epic_issues_spec.rb

@@ -30,7 +30,6 @@ RSpec.describe 'Epic Issues', :js do
 
   before do
     stub_licensed_features(epics: true, subepics: true)
-    stub_const('Epic', ::Epic, transfer_nested_constants: true)
   end
 
   def visit_epic

ee/spec/services/epic_links/create_service_spec.rb

@@ -15,10 +15,6 @@ RSpec.describe EpicLinks::CreateService do
 
     let(:valid_reference) { epic_to_add.to_reference(full: true) }
 
-    before do
-      stub_const('Epic', ::Epic, transfer_nested_constants: true)
-    end
-
     shared_examples 'system notes created' do
       it 'creates system notes' do
         expect { subject }.to change { Note.system.count }.from(0).to(2)