Update python version in setup.cfg

In Epoxy/2025.1 py39 - py312 are the python
versions we are aiming.

Change-Id: I15832375e62118df52bc4dd80738bc4b2b14cd46
diff --git a/setup.cfg b/setup.cfg
index 3e352a0..0962924 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -6,7 +6,7 @@
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://opendev.org/openstack/neutron-tempest-plugin
-python_requires = >=3.6
+python_requires = >=3.9
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,10 +15,10 @@
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
-    Programming Language :: Python :: 3.7
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
+    Programming Language :: Python :: 3.11
+    Programming Language :: Python :: 3.12
 
 [files]
 packages =