change datepicker's format
change datepicker's format

so it matches rails' and they work smoothly together

bitzesty/trade-tariff-admin,bitzesty/trade-tariff-admin,alphagov/trade-tariff-admin,alphagov/trade-tariff-admin,alphagov/trade-tariff-admin,bitzesty/trade-tariff-admin,alphagov/trade-tariff-admin,bitzesty/trade-tariff-admin