Remove order_values argument now that default_scope is simplified

In 94924dc32baf78f13e289172534c2e71c9c8cade the internal default_scope
implementation has changed making it simpler to follow, meaning that the
old usage of with_default_scope has been removed.

With that, order_values was the same argument for both calls to
find_first_with_limit, so remove it and use the existent attribute
for the sake of clarity/simplification.