Remove deprecated method

Rails 5.1.6
method after `save` returned (e.g. the opposite of what it returns now). To maintain the current behavior, use `saved_changes?` instead. (called from set_updater_attribute at /home/ubuntu/bo-shared/vendor/bundle/ruby/2.5.0/bundler/gems/activerecord-userstamp-752f1e30ed8a/lib/active_record/userstamp/stampable.rb:116)