autopkgtest/smoke: don't run boilerplate.t tests

These are really author tests that should be conditional on
RELEASE_TESTING or something like that. They normally require README,
Changes, and the actual module under lib/, but we don't want to
install the last one.

Just nuke the whole test from the temporary tree instead.

There are currently 46 packages failing in the Debian sid archive
because of this test.