removes a gem that hasn't been updated in 15 years

Of course it broke. The newly generated man pages are quite different,
but they appear to render the same. We'll want to go through them again
as we improve our branding & docs.

Author: binford2k

Gemfile

@@ -74,7 +74,7 @@ end
 
 group(:documentation, optional: true) do
   gem 'gettext-setup', '~> 1.0', require: false, platforms: [:ruby]
-  gem 'ronn', '~> 0.7.3', require: false, platforms: [:ruby]
+  gem 'ronn-ng', '~> 0.10.1', require: false, platforms: [:ruby]
   gem 'puppet-strings', require: false, platforms: [:ruby]
   gem 'pandoc-ruby', require: false, platforms: [:ruby]
 end