Refactor inactive draft cleanup rake task to be sidekiq cron job

[murny]

From discovery work found in #1556:

Rake task to cleanup inactive draft objects should be turned into a sidekiq cron job and be run once in a while? For history's sake, this rake task was created before we had sidekiq-cron in our project. But to this date, I highly doubt we ever ran this rake task in production since we implemented this rake task. This could be a big improvement and help us cleanup all the inactive draft objects in our DB.

So as it says, we should refactor the current rake task: https://github.com/ualbertalib/jupiter/blob/integration_postmigration/lib/tasks/jupiter.rake#L6-L24

And instead make this a sidekiq cron job which runs periodically, as I highly doubt we ever used this rake task in production.

[murny]

This has been merged. Closing issue.