Upgrade Rails to version 5.2.0 (#5898)

config/environments/development.rb

@@ -13,13 +13,14 @@ Rails.application.configure do
   config.consider_all_requests_local = true
 
   # Enable/disable caching. By default caching is disabled.
+  # Run rails dev:cache to toggle caching.
   if Rails.root.join('tmp/caching-dev.txt').exist?
     config.action_controller.perform_caching = true
 
     config.cache_store = :redis_store, ENV['REDIS_URL'], REDIS_CACHE_PARAMS
 
     config.public_file_server.headers = {
-      'Cache-Control' => "public, max-age=#{2.days.seconds.to_i}",
+      'Cache-Control' => "public, max-age=#{2.days.to_i}",
     }
   else
     config.action_controller.perform_caching = false