Fix calculation of epic ancestor links

ee/app/presenters/epic_presenter.rb

@@ -133,7 +133,7 @@ class EpicPresenter < Gitlab::View::Presenter::Delegated
       {
         id: epic.id,
         title: epic.title,
-        url: group_epic_path,
+        url: url_builder.epic_path(epic),
         state: epic.state,
         human_readable_end_date: epic.end_date&.to_s(:medium),
         human_readable_timestamp: remaining_days_in_words(epic.end_date, epic.start_date)

ee/changelogs/unreleased/12101-epic-ancestor-links-link-to-self-vs-ancestor-epic.yml

+---
+title: Fix incorrect epic ancestor links
+merge_request: 14092
+author:
+type: fixed

ee/spec/presenters/epic_presenter_spec.rb

@@ -29,6 +29,13 @@ describe EpicPresenter do
       expect(presenter.show_data.keys).to match_array([:initial, :meta])
     end
 
+    it 'has correct ancestors' do
+      metadata     = JSON.parse(presenter.show_data[:meta])
+      ancestor_url = metadata['ancestors'].first['url']
+
+      expect(ancestor_url).to eq "/groups/#{parent_epic.group.full_path}/-/epics/#{parent_epic.iid}"
+    end
+
     it 'returns the correct json schema for epic initial data' do
       data = presenter.show_data(author_icon: 'icon_path')