[#65878680] Remove govuk_class

We no longer need this per gds/puppet@88993ca

I'm using a regex to match the name of the Puppet Master for the additional
shared folder. We no longer have a node/class of just `puppet`. This is a
bit hacky, but not a big deal.
Merge pull request #17 from alphagov/65878680-remove_govuk_class

[#65878680] Remove govuk_class