SSP-2681 Remove *test-tables*.sql

These files weren't actually being used and I wasted my time trying
to figure out what they're doing and whether recent changes were
correct.

Long term it does make sense to embed DDL for SSP's external
tables so our tests can provision those artifacts rather than rely
on out of band db setup. But these files have both that external
DDL and the staging DDL. We definitely don't want to duplicate
the latter, which is also present in
ssp-data-importer-impl/src/main/resources/sql. So for now these files
really are just noise.