Change-Id: I8571774c1fcb71bd07f0339a9c9e0f83a5eac3be

Update the URL to the upper-constraints file to point to the redirect
rule on releases.openstack.org so that anyone working on this branch
will switch to the correct upper-constraints list automatically when
the requirements repository branches.

Until the requirements repository has as stable/victoria branch, tests will
continue to use the upper-constraints list on master.

Change-Id: If9946c3dd78752eaa3548de0cec45517a043e7bc

Change-Id: Ibe1a965dbcfb04d6e53f89b010790d5c045b50d1

py38 jobs (on ubuntu-focal) started to fail (see the relevant github
issue [1]) due to recent virtualenv release (20.26.4; which bundles
setuptools).

setuptools is bundled in virtualenv, so it has to be capped via the
virtualenv package. tox also needed to be capped (<4) as gate uses
tox 3.28.0, but with capping virtualenv we pull in latest tox as well,
which would cause other errors.

Furthermore, lower-constraints jobs are not supported anymore and are
removed from most of the branches, so let's remove here as well to
unblock the gate.

[1] pypa/setuptools#4483

Change-Id: I521660d9ab6996d0ee7b475c5dcd183889a8b14e

…/victoria