In https://gitlab.com/groups/gitlab-com/gl-infra/data-access/durability/-/epics/9, we're migrating Redis Sessions (Redis sentinel) to a new Redis Cluster Sessions to horizontally scale the CPU.
Once the gprd migration https://gitlab.com/gitlab-com/gl-infra/production/-/issues/19252 is done, we can remove the migration helpers, Gitlab::Redis::ClusterSessions and its related feature flags.
Part of cleanup post migration in https://gitlab.com/gitlab-com/gl-infra/data-access/durability/team/-/issues/34

Changelog: other