test: Install Appraisal dependencies

Gemfile

@@ -9,6 +9,7 @@ if ENV['DEVEL'] == '1'
 
   gem 'activeadmin', ENV.fetch('ACTIVEADMIN_VERSION')
   gem 'activeadmin_quill_editor', path: './'
+  gem 'appraisal', '~> 2.4'
 
   if rails_ver.start_with?('7.0')
     gem 'concurrent-ruby', '1.3.4'