[9.18] chg: ci: Drop removed system tests from cross-version-config-tests

The cross-version-config-tests job fails when a system test is removed
from the upcoming release. To avoid this, remove the system test also
from the $BIND_BASELINE_VERSION.

See the failure mode at https://gitlab.isc.org/isc-projects/bind9/-/jobs/4668947.

Backport of MR !9413

Merge branch 'backport-mnowak/remove-dialup-from-cross-version-config-tests-job-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!9416