Extract EE code in spec/factories/notes.rb

Uses FactoryBot.modify to override the factory and moved the file to the
ee folder

ee/spec/factories/notes.rb

+# frozen_string_literal: true
+
+FactoryBot.modify do
+  factory :note do
+    trait :on_epic do
+      noteable { create(:epic) }
+      project nil
+    end
+  end
+end
+
+FactoryBot.define do
+  factory :note_on_epic, parent: :note, traits: [:on_epic]
+end

spec/factories/notes.rb

@@ -14,7 +14,6 @@ FactoryBot.define do
     factory :note_on_merge_request,      traits: [:on_merge_request]
     factory :note_on_project_snippet,    traits: [:on_project_snippet]
     factory :note_on_personal_snippet,   traits: [:on_personal_snippet]
-    factory :note_on_epic,               traits: [:on_epic]
     factory :system_note,                traits: [:system]
 
     factory :discussion_note, class: DiscussionNote
@@ -134,11 +133,6 @@ FactoryBot.define do
       project nil
     end
 
-    trait :on_epic do
-      noteable { create(:epic) }
-      project nil
-    end
-
     trait :system do
       system true
     end