Upgrade Rails to 8.1.3

test/system/tasks_test.rb

@@ -1,9 +1,5 @@
 require 'application_system_test_case'
 
-# NOTE: remove constant to avoid warnings due to double loading of
-# rails/tasks/statistics.rake. To be removed after upgrade to Rails 8.1.
-Object.send(:remove_const, :STATS_DIRECTORIES)
-
 Rails.application.load_tasks
 # NOTE: for some reason task for checking pending migrations messes up
 # transaction when run during test. It causes all DB changes made before its