Allow concurrency when using Puma

changelogs/unreleased/53362-allow-concurrency-in-puma.yml

+---
+title: Allow Rails concurrency when running in Puma
+merge_request: 22751
+author:
+type: performance

config/environments/development.rb

@@ -45,4 +45,6 @@ Rails.application.configure do
 
   # Do not log asset requests
   config.assets.quiet = true
+
+  config.allow_concurrency = defined?(::Puma)
 end

config/environments/production.rb

@@ -83,5 +83,5 @@ Rails.application.configure do
 
   config.eager_load = true
 
-  config.allow_concurrency = false
+  config.allow_concurrency = defined?(::Puma)
 end