gitlab_group_access_token `expires_at` default no longer works

The default for expires_at is documented to be never however this has stopped working. It would appear that a recent change to GitLab means if you try to create a token with no expiry (even via the UI) it gets a default of 1 year applied. This results in terraform trying to replace the token on every run. eg.

 ~ created_at   = "2023-05-19T09:47:51Z" -> (known after apply)
 - expires_at   = "2024-05-18" -> null # forces replacement