Change role of the export:mappings job in schedule.rb
Change role of the export:mappings job in schedule.rb

This seems to be working, but I'm not quite sure why. Anyway, the job
jobs use :backend as the role, and that's what's being set in
govuk-app-deployment, so just change this to be consistent (and hope
nothing goes wrong!).

alphagov/whitehall,alphagov/whitehall,alphagov/whitehall,alphagov/whitehall