Remove Python 3.8 support

Python 3.8 was removed from the tested runtimes for 2024.2[1] and has
not been tested since then.

Also add a few newer versions which are part of the tested runtimes for
2025.1.

[1] https://governance.openstack.org/tc/reference/runtimes/2024.2.html

Change-Id: I3f5bbc0e12c7cf9a282d73d04ee2d2bfa78d9748

Author: kajinamit

releasenotes/notes/remove-py38-4240ec2f24969054.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 3.8 support was dropped. The minimum version of Python now supported
+    is Python 3.9.

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = [email protected]
 home_page = https://docs.openstack.org/ovn-octavia-provider/latest/
-python_requires = >=3.8
+python_requires = >=3.9
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,8 +15,10 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    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 =