Remove allow_concurrency as a flag

The flag was mainly used to add a Rack::Lock middleware to
the stack, but the only scenario the lock is desired is in
development.

If you are deploying on a not-threaded server, the Rack::Lock
does not provide any benefit since you don't have concurrent
accesses. On the other hand, if you are on a threaded server,
you don't want the lock, since it defeats the purpose of using
a threaded server.

If there is someone out there, running on a thread server
and does want a lock, it can be added to your environment
as easy as: `use Rack::Lock`

1 files changed, 2 insertions, 2 deletions

diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 9c9ed0cd6b..34b460d0a7 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -87,8 +87,8 @@ module ApplicationTests
       assert !middleware.include?("ActiveRecord::QueryCache")
     end
 
-    test "removes lock if allow concurrency is set" do
-      add_to_config "config.allow_concurrency = true"
+    test "removes lock if cache classes is set" do
+      add_to_config "config.cache_classes = true"
       boot!
       assert !middleware.include?("Rack::Lock")
     end