Remove doorkeeper workaround (#39336)

config/application.rb

@@ -111,6 +111,9 @@ module Mastodon
     end
 
     config.to_prepare do
+      Doorkeeper::Application.include ApplicationExtension
+      Doorkeeper::AccessGrant.include AccessGrantExtension
+      Doorkeeper::AccessToken.include AccessTokenExtension
       Devise::FailureApp.include AbstractController::Callbacks
       Devise::FailureApp.include Localized
     end

config/initializers/doorkeeper.rb

@@ -179,9 +179,3 @@ Doorkeeper.configure do
   # WWW-Authenticate Realm (default "Doorkeeper").
   # realm "Doorkeeper"
 end
-
-Rails.application.reloader.to_prepare do
-  Doorkeeper.config.application_model.include ApplicationExtension
-  Doorkeeper.config.access_grant_model.include AccessGrantExtension
-  Doorkeeper.config.access_token_model.include AccessTokenExtension
-end