Ignore `user_details.provisioned_by_group_at` column

What does this MR do and why?

We want to remove user_details.provisioned_by_group_at column, see why #412437 (closed).

Since !122871 (merged) we don't use this column anymore.

This MR prepare this column for its removal as per the guide https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#dropping-columns

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