Enable gfm_form on new epic form

This is to enable suggestions on the description
field.

ee/app/controllers/groups/autocomplete_sources_controller.rb

@@ -46,10 +46,9 @@ class Groups::AutocompleteSourcesController < Groups::ApplicationController
 
   # rubocop: disable CodeReuse/ActiveRecord
   def target
-    case params[:type]&.downcase
-    when 'epic'
-      EpicsFinder.new(current_user, group_id: @group.id).find_by(iid: params[:type_id])
-    end
+    QuickActions::TargetService
+      .new(nil, current_user, group: @group)
+      .execute(params[:type], params[:type_id])
   end
   # rubocop: enable CodeReuse/ActiveRecord
 end

ee/app/views/groups/epics/new.html.haml

+- @gfm_form = true
+- @noteable = Epic.new
 - add_to_breadcrumbs _("Epics"), group_epics_path(@group)
 - breadcrumb_title _("New")
 - page_title _("New epic")