FIX: Fix rake db:create after zeitwerk changes

Post-zeitwerk, rails has deprecated autoloading modules during
initialization and forces all autoloaded modules to be reloaded after
initialization.

Requiring the file explicitly prevents autoloading and therefore
prevents the state on SiteSetting being trashed which was causing the
problem here.

config/initializers/005-site_settings.rb

@@ -6,6 +6,10 @@
 Discourse.git_version
 
 if GlobalSetting.skip_redis?
+  # Requiring this file explicitly prevents it from being autoloaded and so the
+  # provider attribute is not cleared
+  require File.expand_path('../../../app/models/site_setting', __FILE__)
+
   require 'site_settings/local_process_provider'
   Rails.cache = Discourse.cache
   SiteSetting.provider = SiteSettings::LocalProcessProvider.new