Ignore approvals_before_merge column
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The `approvals_before_merge` field has been made redundant within:
- Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/11132.
- Merge request: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/16121
Within this issue we should:
- Make sure that `approvals_before_merge` replacement works properly and is not used in the database!
- Ignore the column, which is the first step of [the 3-release approach of column removal](https://docs.gitlab.com/ee/development/avoiding_downtime_in_migrations.html#dropping-columns)
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