Merge pull request #10710 from demarches-simplifiees/remove-unused-hidden-at-for-dossiers-ldu

[Tech] Retirer la colonne obsolète 'hidden_at' des dossiers (part 1)

spec/factories/dossier.rb

@@ -112,10 +112,6 @@ FactoryBot.define do
       archived { false }
     end
 
-    trait :discarded do
-      hidden_at { Time.zone.now }
-    end
-
     trait :hidden_by_expired do
       hidden_by_expired_at { 1.day.ago }
       hidden_by_reason { DeletedDossier.reasons.fetch(:expired) }