Revert "Merge pull request #73 from alphagov/remove_access_to_non_declarable_commodities"

This reverts commit 39fac84cb127d6daec29727a86d4384bc35fbab5, reversing
changes made to 88962a28166ccba17e7c700f144f313a22199edb.

This caused trade-tariff-suite to fail against production. trade-tariff-suite is
now set up to run against CI, so we'll get a tighter feedback loop when a change
is made which breaks anything.