Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/348307

After token encryption executed in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/75417. We can
start deprecation process for
"static_objects_external_storage_auth_token".

* Ignore static_objects_external_storage_auth_token field
* Change encryption mode to 'required'

Changelog: changed