Updates serialization spec

Author: picandocodigo

Diff for: elasticsearch-model/spec/elasticsearch/model/adapters/active_record/serialization_spec.rb

@@ -52,9 +52,10 @@
     end
 
     context 'when a document is updated' do
-
       before do
-        article.update_attributes(title: 'UPDATED', status: 'yellow')
+        article.update_attribute(title: 'UPDATED')
+        article.update_attribute(status: 'yellow')
+
         ArticleWithCustomSerialization.__elasticsearch__.refresh_index!
       end