Merge pull request #2253 from zvkemp/disable-logging-docs

[docs] disable logger via /dev/null instead of AS::N.unsubscribe

Author: bf4

docs/general/logging.md

@@ -16,6 +16,5 @@ ActiveModelSerializers.logger = Logger.new(STDOUT)
 You can also disable the logger, just put this in `config/initializers/active_model_serializers.rb`:
 
 ```ruby
-require 'active_model_serializers'
-ActiveSupport::Notifications.unsubscribe(ActiveModelSerializers::Logging::RENDER_EVENT)
+ActiveModelSerializers.logger = Logger.new(IO::NULL)
 ```