[ci] our database backcompat tests have been broken for a while
Created by: ggilmore
Our database back compat script looks for all packages that import cmd/frontend/db/dbtesting, but the cmd/frontend/db/dbtesting package hasn't exist for a while. It was extracted out and renamed to https://github.com/sourcegraph/sourcegraph/tree/master/internal/db/dbtesting as part of the management console work.
This implies that this test has been broken for over a year. Going forward, we should add check to this script to make sure that at least one package is returned from that query.