Duty Expression: add exception for Supplementary unit
Duty Expression: add exception for Supplementary unit

alphagov/trade-tariff-frontend,alphagov/trade-tariff-frontend,alphagov/trade-tariff-frontend,bitzesty/trade-tariff-frontend,bitzesty/trade-tariff-frontend,bitzesty/trade-tariff-frontend,bitzesty/trade-tariff-frontend,alphagov/trade-tariff-frontend