EE seems to have had an outdated schema at some point, leading to some
environments not having the right columns in place. This adjusts the
migration for `issues.closed_at` so it takes care of those cases,
ensuring data can be migrated properly.
Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/4803
In the event of Sidekiq jobs getting lost there may be some rows left to
migrate. This migration ensures any remaining jobs are completed and
that all data has been migrated.
This fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/41595