Fix upgrade failure in EE displaying license

When upgrading to 12.8 EE, the initializer might fail with
`NoMethodError: undefined method `pluralize' for LicenseHelper:Module`
if the license neared expiry. This happened
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/24998 changed the
database check so that the license warning would actually be displayed,
but inside an initializer `pluralize` is not available.

The easiest way to fix this now is to revert the database check to the
original version.

Closes https://gitlab.com/gitlab-org/gitlab/issues/207737

changelogs/unreleased/sh-fix-license-check-migration.yml

+---
+title: Fix upgrade failure in EE displaying license
+merge_request: 25788
+author:
+type: fixed

config/initializers/0_license.rb

@@ -10,7 +10,7 @@ Gitlab.ee do
   end
 
   # Needed to run migration
-  if Gitlab::Database.cached_table_exists?('licenses')
+  if ActiveRecord::Base.connected? && ActiveRecord::Base.connection.table_exists?('licenses')
     message = LicenseHelper.license_message(signed_in: true, is_admin: true, in_html: false)
     if ::License.block_changes? && message.present?
       warn "WARNING: #{message}"