Switch testing to Antelope testing runtime

Updating the testing template to Antelope testing runtime:
https://governance.openstack.org/tc/reference/runtimes/2023.1.html

Change-Id: I2e0b6d679d1262bd63b0f9375ec28eb2affa135d

.zuul.yaml

@@ -8,10 +8,10 @@
         - openstack-tox-pep8
         - openstack-tox-py38
         - openstack-tox-py39
-        - openstack-tox-py310:
-            voting: false
+        - openstack-tox-py310
     gate:
       jobs:
         - openstack-tox-pep8
         - openstack-tox-py38
         - openstack-tox-py39
+        - openstack-tox-py310

setup.cfg

@@ -19,6 +19,7 @@ classifier =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
 
 [files]
 packages =

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 3.18.0
-envlist = py{39,36},pep8,pip-check-reqs
+envlist = py3,pep8,pip-check-reqs
 skipsdist = True
 ignore_basepython_conflict = True