Update “handle encrypted hiera data” manual page
Update “handle encrypted hiera data” manual page

This commit updates the “handle encrypted hiera data” manual page with both general updates and a rewrite of the GPG key and Puppet Master sections to reflect current processes.

alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs,alphagov/govuk-developer-docs