On-call: Remove the 'access to govuk_mirror-puppet' line
On-call: Remove the 'access to govuk_mirror-puppet' line

- The `govuk_mirror-puppet` repo is archived, so no-one new can add
  themselves to it. Also they don't need to, because the mirrors
  architecture has
  [changed](https://docs.publishing.service.gov.uk/manual/fall-back-to-mirror.html#hosting)
  (https://github.com/alphagov/govuk-developer-docs/pull/1835).

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