Fix with_comment format in annotate_models_rake (#560)

* :with_comment option is flag
* It should use `true?` instead of `fallback`.

Author: yhirano55

lib/tasks/annotate_models.rake

@@ -47,7 +47,7 @@ task annotate_models: :environment do
   options[:ignore_routes] = ENV.fetch('ignore_routes', nil)
   options[:hide_limit_column_types] = Annotate.fallback(ENV['hide_limit_column_types'], '')
   options[:hide_default_column_types] = Annotate.fallback(ENV['hide_default_column_types'], '')
-  options[:with_comment] = Annotate.fallback(ENV['with_comment'], '')
+  options[:with_comment] = Annotate.true?(ENV['with_comment'])
 
   AnnotateModels.do_annotations(options)
 end