Update TOX_CONSTRAINTS_FILE for stable/2023.2

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/2023.2 branch, tests will
continue to use the upper-constraints list on master.

Change-Id: Ic862dadbb0ca77b0a88b0a2bfc5903354a21e780

.gitreview

@@ -2,3 +2,4 @@
 host=review.opendev.org
 port=29418
 project=openstack/python-watcherclient.git
+defaultbranch=stable/2023.2

tox.ini

@@ -10,7 +10,7 @@ install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2023.2}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
 allowlist_externals =
@@ -42,7 +42,7 @@ commands =
 [testenv:docs]
 basepython = python3
 deps =
-  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2023.2}
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html