Update danger for documentation throughput
documentation is now a throughput label, as shown at https://about.gitlab.com/handbook/engineering/management/throughput/, so we should update Danger so that it doesn't complain on docs MRs.
documentation is now a throughput label, as shown at https://about.gitlab.com/handbook/engineering/management/throughput/, so we should update Danger so that it doesn't complain on docs MRs.