Keep the `parent` method in `Project`

app/models/concerns/group_descendant.rb

@@ -3,14 +3,6 @@ module GroupDescendant
     expand_hierarchy_for_child(self, self, hierarchy_base)
   end
 
-  def parent
-    if self.is_a?(Project)
-      namespace
-    else
-      super
-    end
-  end
-
   def expand_hierarchy_for_child(child, hierarchy, hierarchy_base)
     if child.parent.nil? && hierarchy_base.present?
       raise ArgumentError.new('specified base is not part of the tree')

app/models/project.rb

@@ -1521,6 +1521,10 @@ class Project < ActiveRecord::Base
     map.public_path_for_source_path(path)
   end
 
+  def parent
+    namespace
+  end
+
   def parent_changed?
     namespace_id_changed?
   end