[stable-only] Update TOX_CONSTRAINTS_FILE for stable/zed

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/zed branch, tests will
continue to use the upper-constraints list on master.

Change-Id: I9dad37b404c41f6837bff49c8dcb0d9d254d37f7

Author: openstackadmin

tox.ini

@@ -26,7 +26,7 @@ setenv =
 # TODO(stephenfin): Remove once we bump our upper-constraint to SQLAlchemy 2.0
   SQLALCHEMY_WARN_20=1
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/zed}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
 extras =
@@ -200,7 +200,7 @@ description =
 # Note that we don't use {[testenv]deps} for deps here because we don't want
 # to install (test-)requirements.txt for docs.
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/zed}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 extras =