Update test

spec/models/form/sales/questions/staircase_last_date_spec.rb

@@ -1,6 +1,6 @@
 require "rails_helper"
 
-RSpec.describe Form::Sales::Questions::StaircaseInitialDate, type: :model do
+RSpec.describe Form::Sales::Questions::StaircaseLastDate, type: :model do
   subject(:question) { described_class.new(question_id, question_definition, page) }
 
   let(:question_id) { nil }