CI: Disable jjb-latest tox test

CI: Disable jjb-latest tox test

JJB v5.x released this morning (April 12, 2023) and started breaking the
jjb-latest validation test. As the test is a canary test, it did the
correct thing and broke our builds alerting us to the issue.

This disables the test so that other work is unblocked until such time
as we can determine the correct way forward with fixes and can turn this
test back on.

Issue: RELENG-4686
Change-Id: I94f6e944356c5aabb75434165a738b4d9336d818
Signed-off-by: Andrew Grimberg <agrimberg@linuxfoundation.org>