Replace Warden test helpers with Devise ones

spec/requests/epp/domain/update/nameserver_add_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe 'EPP domain:update' do
   subject(:response_description) { response_xml.css('result msg').text }
 
   before :example do
-    login_as user
+    sign_in user
 
     allow(Domain).to receive(:nameserver_required?).and_return(false)
     Setting.ns_min_count = 2

spec/requests/epp/domain/update/nameserver_remove_spec.rb

@@ -9,7 +9,7 @@ RSpec.describe 'EPP domain:update' do
   subject(:response_description) { response_xml.css('result msg').text }
 
   before :example do
-    login_as user
+    sign_in user
     allow(Domain).to receive(:nameserver_required?).and_return(false)
   end
 

spec/requests/epp/domain/update/registrant_change/same_as_current_spec.rb

@@ -8,7 +8,7 @@ RSpec.describe 'EPP domain:update' do
   let!(:domain) { create(:domain, name: 'test.com', registrant: registrant) }
 
   before :example do
-    login_as user
+    sign_in user
   end
 
   context 'when registrant change confirmation is enabled' do

spec/requests/epp/domain/update/registrant_change/verified_spec.rb

@@ -10,7 +10,7 @@ RSpec.describe 'EPP domain:update' do
   let!(:new_registrant) { create(:registrant, code: 'new-code') }
 
   before :example do
-    login_as user
+    sign_in user
   end
 
   context 'when registrant change confirmation is enabled' do

spec/requests/epp/domain/update/status_spec.rb

@@ -20,7 +20,7 @@ RSpec.describe 'EPP domain:update' do
   }
 
   before :example do
-    login_as user
+    sign_in user
   end
 
   context 'when domain has both SERVER_DELETE_PROHIBITED and PENDING_UPDATE statuses' do