Backport EE changes to ProjectSearchResults

EE made some changes to the project_ids_relation method, but these were
not backported to CE.

lib/gitlab/project_search_results.rb

@@ -134,9 +134,11 @@ module Gitlab
       project.repository.commit(key) if Commit.valid_hash?(key)
     end
 
+    # rubocop: disable CodeReuse/ActiveRecord
     def project_ids_relation
-      project
+      Project.where(id: project).select(:id).reorder(nil)
     end
+    # rubocop: enabled CodeReuse/ActiveRecord
 
     def filter_milestones_by_project(milestones)
       return Milestone.none unless Ability.allowed?(@current_user, :read_milestone, @project)