Simplify the metadata.rb to resolve cookstyle warnings

Signed-off-by: Tim Smith <tsmith@chef.io>

kitchen.dokken.yml

+---
 driver:
   name: dokken
   privileged: true # because Docker and SystemD/Upstart

metadata.rb

@@ -5,9 +5,8 @@ license 'Apache-2.0'
 description 'Configures apt and apt caching.'
 version '7.2.0'
 
-%w(ubuntu debian).each do |os|
-  supports os
-end
+supports 'ubuntu'
+supports 'debian'
 
 source_url 'https://github.com/chef-cookbooks/apt'
 issues_url 'https://github.com/chef-cookbooks/apt/issues'