Fix query on clean_discarded_statuses

[tribela]

irb(main):001:0> Status.discarded.where('deleted_at <?', 30.days.ago).to_sql
=> "SELECT \"statuses\".* FROM \"statuses\" WHERE \"statuses\".\"deleted_at\" IS NULL AND \"statuses\".\"deleted_at\" IS NOT NULL AND (deleted_at <'2022-02-16 07:17:47.866763') ORDER BY \"statuses\".\"id\" DESC"
irb(main):002:0> Status.with_discarded.where('deleted_at < ?', 30.days.ago).to_sql
=> "SELECT \"statuses\".* FROM \"statuses\" WHERE (deleted_at < '2022-02-16 07:20:11.330404') ORDER BY \"statuses\".\"id\" DESC"
irb(main):020:0> Status.unscoped.discarded.to_sql
=> "SELECT \"statuses\".* FROM \"statuses\" WHERE \"statuses\".\"deleted_at\" IS NOT NULL"

Previous query contains deleted is null and deleted is not null which is completely impossible.