Remove unnecessary spec (#615)
Remove unnecessary spec (#615)

Devise gem already tests the last_sign_in_at. 

It's behaviour has also changed to be nil in users' first session.
https://github.com/plataformatec/devise/blob/v4.4.3/lib/devise/models/trackable.rb#L37
ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture,ministryofjustice/tax-tribunals-datacapture