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: Ie6a89b7f9d336753095c7237d1a24cac56b3f93d

.gitreview

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

tox.ini

@@ -12,7 +12,7 @@ setenv = VIRTUAL_ENV={envdir}
          LC_ALL=C
          PYTHONWARNINGS=default::DeprecationWarning
 usedevelop = True
-deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/2023.2}
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 # Delete bytecodes from normal directories before running tests.
@@ -46,7 +46,7 @@ commands =
 
 [testenv: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/2023.2}
   -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
@@ -61,7 +61,7 @@ commands =
 
 [testenv:releasenotes]
 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 -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html