Fix ee css bundles not loading

It turns out that prefer_specialized_assets intializer needs to be
placed correctly. Otherwise when we add new initializers, it will be
shifted and hence cause it to be executed too late (after we start
accepting requests)

Changelog: fixed

config/application.rb

@@ -524,7 +524,7 @@ class Application < Rails::Application
     # app/assets/stylesheets/example.scss
     #
     # The jh/ version will be preferred.
-    initializer :prefer_specialized_assets, after: :append_assets_path do |app|
+    initializer :prefer_specialized_assets, after: :append_assets_path, before: :build_middleware_stack do |app|
       Gitlab.extensions.each do |extension|
         %w[images javascripts stylesheets].each do |path|
           app.config.assets.paths.unshift("#{config.root}/#{extension}/app/assets/#{path}")