Only allow Sidekiq 5.2+ and 6 for now
Sidekiq 7 has some breaking changes (https://github.com/mperham/sidekiq/blob/main/docs/7.0-Upgrade.md), and the dependency on redis-client v5+ would also require that we upgrade to Rails 7.
Sidekiq 7 has some breaking changes (https://github.com/mperham/sidekiq/blob/main/docs/7.0-Upgrade.md), and the dependency on redis-client v5+ would also require that we upgrade to Rails 7.