Replace UTF-8 whitespace in comment

There is an UTF-8 whitespace which blows up older puppet-lint versions. Replace with space character

./modules/apt/manifests/source.pp
/usr/lib/ruby/vendor_ruby/puppet-lint/checks.rb:23:in `split': invalid byte sequence in US-ASCII (ArgumentError)
	from /usr/lib/ruby/vendor_ruby/puppet-lint/checks.rb:23:in `load_data'
	from /usr/lib/ruby/vendor_ruby/puppet-lint/checks.rb:53:in `run'
	from /usr/lib/ruby/vendor_ruby/puppet-lint.rb:174:in `run'
	from /usr/lib/ruby/vendor_ruby/puppet-lint/bin.rb:59:in `block in run'
	from /usr/lib/ruby/vendor_ruby/puppet-lint/bin.rb:56:in `each'
	from /usr/lib/ruby/vendor_ruby/puppet-lint/bin.rb:56:in `run'
	from /usr/bin/puppet-lint:7:in `<main>'
Detected error