Set proper type for jbuilder option to prevent a warning with Thor >= 0.19.3

See rails/thor#435, right now we got a warning
>Expected string default value for '--jbuilder'; got true (boolean)

Author: ojab

lib/generators/rails/scaffold_controller_generator.rb

@@ -6,7 +6,7 @@ module Generators
     class ScaffoldControllerGenerator
       source_paths << File.expand_path('../templates', __FILE__)
 
-      hook_for :jbuilder, default: true
+      hook_for :jbuilder, type: :boolean, default: true
     end
   end
 end