Use upper-constraint in doc generation

Currently doc jobs are broken because the latest sphinx 7.2.0 is not
compatible with the latest release of openstackdocstheme.

This updates the docs/releasenotes target to use the global upper
constraints to avoid that issue.

Also, the following flake8 error is fixed by this change.

cliff/tests/test_formatters_table.py:53:10: E721 do not compare types,
for exact checks use `is` / `is not`, for instance checks use
`isinstance()`

Change-Id: Ia923ba1d0e2cf3327317e142cfa38470d9f053d2

cliff/tests/test_formatters_table.py

@@ -50,7 +50,7 @@ def _table_tester_helper(tags, data, extra_args=None):
     if extra_args is None:
         # Default to no CLI arguments
         parsed_args = args()
-    elif type(extra_args) == args:
+    elif isinstance(extra_args, args):
         # Use the given CLI arguments
         parsed_args = extra_args
     else:

tox.ini

@@ -45,7 +45,9 @@ deps = os:openstack/python-openstackclient:python-openstackclient
 commands = {toxinidir}/integration-tests/openstackclient-tip.sh {envdir}
 
 [testenv:docs]
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:cover]