Remove unnecessary gem dependency

Author: Michael Chmielewski

Gemfile

@@ -4,10 +4,9 @@ group :development, :unit_tests do
   gem 'rake',           :require => false
 end
 group :system_tests do
-  gem 'busser-serverspec',     :require => false
   gem 'serverspec',     :require => false
-  gem 'test-kitchen',    :require => false
-  gem 'kitchen-salt',  :require => false
+  gem 'test-kitchen',   :require => false
+  gem 'kitchen-salt',   :require => false
   gem 'kitchen-docker', :require => false
 end