Cop idea: Prefer new syntax for sending delayed emails

## Describe the solution you'd like

https://github.com/sidekiq/sidekiq/wiki/Active-Job#action-mailer

```ruby
# bad
UserMailer.delay_for(1.hour).welcome_email(@user.id)
UserMailer.delay_until(5.days.from_now).welcome_email(@user.id)

# good
UserMailer.welcome_email(@user).deliver_later(wait: 1.hour)
UserMailer.welcome_email(@user).deliver_later(wait_until: 5.days.from_now)
```