rename lambda references to use shorthand syntax

config/application.rb

@@ -21,7 +21,7 @@ module Danbooru
     config.action_mailer.delivery_method = :smtp
     config.action_mailer.smtp_settings = {:enable_starttls_auto => false}
     config.action_mailer.perform_deliveries = true
-    config.log_tags = [lambda {|req| "PID:#{Process.pid}"}]
+    config.log_tags = [->(req) {"PID:#{Process.pid}"}]
     config.action_controller.action_on_unpermitted_parameters = :raise
     config.force_ssl = true