Replace assign_attributes with public_sent

lib/gitlab/import_export/relation_factory.rb

@@ -134,11 +134,11 @@ module Gitlab
         return object unless value
 
         references.each do |key|
-          attribute = key.delete_suffix('_id').to_sym
+          attribute = "#{key.delete_suffix('_id')}=".to_sym
           next unless object.respond_to?(key) && object.respond_to?(attribute)
 
           if object.read_attribute(key) == value&.id
-            object.assign_attributes(attribute => value)
+            object.public_send(attribute, value) # rubocop:disable GitlabSecurity/PublicSend
           end
         end