Use "publishing.service.gov.uk" as the example production hostname
Use "publishing.service.gov.uk" as the example production hostname

- I was just explaining Plek to someone and referred to the README,
  only to notice that it still referenced "production.alphagov.co.uk"
  rather than "publishing.service.gov.uk" for production hosts.
  Testing this on Integration, `Plek.new.find('frontend')` returns
  "https://frontend.integration.publishing.service.gov.uk", so I
  assume it works the same way in production.

alphagov/plek