Add python 3.11 unit test job

Python 3.11 is going to be added as required
python version testing[1] so testing it in
advance is good idea.

[1] https://governance.openstack.org/tc/reference/runtimes/2024.1.html#python-runtimes-for-2024-1

Change-Id: I77c51657d67b644ece30589f26bb795929f25bc4
diff --git a/setup.cfg b/setup.cfg
index beaf9b4..bb1ced5 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -18,6 +18,7 @@
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
+    Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython