[Nanobox] Apply Release Notes Changes (#5670)

Apparently I missed some things in earlier commits/releases that needed to be applied to the Nanobox setup. All minor things, nothing that breaks anything, but still best to get them in place.

- Move cron jobs to their own component, so the Sidekiq component can be scaled up to multiple instances without causing issues with running the same cron job multiple times at once.
- Update cron jobs to the latest requirements, removing extraneous ones
- Add new variables to `.env.nanobox`
- Update Nginx to use correct cache header directives