Remove dependency on govuk_setenv
Remove dependency on govuk_setenv

We're probably not going to use this on the CI boxes, so we should just
set the desired environment variables explicitly.

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