Moves supported python runtimes from version 3.8 to 3.10

Within 2023.2 python version 3.9 and 3.10 are the
supported python runtimes [1].
[1] https: //review.opendev.org/c/openstack/governance/+/872232

Change-Id: Ibabaaf286ca4ce942908086e490929900ccf7c95

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/oslo.log/latest
-python_requires = >=3.8
+python_requires = >=3.9
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,8 +15,8 @@ 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 :: Only
     Programming Language :: Python :: Implementation :: CPython