fix low ruby version support bug

app/libs/custom_sortable.rb

@@ -17,7 +17,7 @@ module CustomSortable
     relations.send(order_method, "#{sort_by} #{sort_direction}")
   end
 
-  def multiple_custom_sort(relations, **opts)
+  def multiple_custom_sort(relations, opts)
     opts.each do |sort_by, sort_direction|
       relations = custom_sort(relations, sort_by, sort_direction)
     end