Stop generating last_update, and generate pretty-printed JSONs

lib/quby/compiler/instance.rb

@@ -51,7 +51,7 @@ module Quby
             quby_frontend_v2: Output.new(
               key: :quby_frontend_v2,
               filename: "quby-frontend-v2.json",
-              content: JSON.pretty_generate(Outputs::QubyFrontendV2Serializer.new(questionnaire).as_json),
+              content: Outputs::QubyFrontendV2Serializer.new(questionnaire).to_json,
             ),
           },
         }