Fix `rack-timeout` require

We need to require `rack/timeout/base`
according to documentation to not preload
Rack::Timeout. This allows us to configure
Rack::Timeout on our own.

Gemfile

@@ -164,7 +164,8 @@ gem 'diff_match_patch', '~> 0.1.0'
 
 # Application server
 gem 'rack', '~> 2.0.9'
-gem 'rack-timeout', '~> 0.5.1'
+# https://github.com/sharpstone/rack-timeout/blob/master/README.md#rails-apps-manually
+gem 'rack-timeout', '~> 0.5.1', require: 'rack/timeout/base'
 
 group :unicorn do
   gem 'unicorn', '~> 5.5'

changelogs/unreleased/update-rack-timeout.yml

 ---
 title: Update `rack-timeout` to `0.5.2`
-merge_request: 36071
+merge_request: 36289
 author:
 type: changed

config/initializers/rack_timeout.rb

@@ -10,8 +10,6 @@
 # logged and we should fix the potential timeout issue in the code itself.
 
 if Gitlab::Runtime.puma? && !Rails.env.test?
-  require 'rack/timeout/base'
-
   Rack::Timeout::Logger.level = Logger::ERROR
 
   Gitlab::Application.configure do |config|