We don't need tox nor tell our users to use it when doing kolla builds.
Tox is going away from base infra images (it is already gone from
aarch64 ones).
Depends-on: https://review.opendev.org/713134
Co-authored-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Change-Id: Ib1d97a783951ac42740ebf91bcc6ecaf2bf70853
c089eab392