Enable threaded I/O on redis-sidekiq gprd

Now that the upgrade to Redis 6 is complete https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12957, we can enable threaded I/O.

We'll need to perform a controlled rollout, since changing this parameter will require a process restart. Disabling chef should not be necessary, as config changes no longer trigger process restarts.

The reconfigure however is expected to do so. So we'll want to failover before the reconfigure.