chore: Use feature_flags attribute instead of settings_flags (#6820)

* chore: Use feature_flag instead of settings_flag

* Remove unnecessary changes

spec/factories/accounts.rb

@@ -4,7 +4,6 @@ FactoryBot.define do
   factory :account do
     sequence(:name) { |n| "Account #{n}" }
     status { 'active' }
-    custom_email_domain_enabled { false }
     domain { 'test.com' }
     support_email { 'support@test.com' }
   end