mruby-data: update a comment (there's no Data.new) [ci skip]

mrbgems/mruby-data/src/data.c

@@ -203,7 +203,7 @@ make_data_class(mrb_state *mrb, mrb_value members, struct RClass *klass)
  *  are defined for this generated class.
  *
  *     # Create a structure named by its constant
- *     Customer = Data.new(:name, :address)     #=> Customer
+ *     Customer = Data.define(:name, :address)  #=> Customer
  *     Customer.new("Dave", "123 Main")         #=> #<data name="Dave", address="123 Main">
  */
 static mrb_value