Update use of `low` priority Zendesk queue
Update use of `low` priority Zendesk queue

We have been using this queue for product related tickets but we now
have a new group to triage them too. This means 2nd line can use the
low queue for other purposes. Also made it clearer when to close
tickets.

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