Our documentation showed that Victoria, Ussuri and Train are the
supported releases by tempest's master, which wasn't the case.
It also showed that tempest is compatible with python 3.6, 3.7
and 3.8. We dropped py 3.6 and 3.7 support by [1].
[1] https://review.opendev.org/c/openstack/tempest/+/843182
Closes-Bug: #1976282
Change-Id: I0ccfa824f08cbdf58f26a142dac3a0881605ef08