Support py3.12 and drop py3.8

As per the current release tested runtime, we test
from python 3.9 till python 3.12 so updating the same
in python classifier in setup.cfg

Also, dropping the python3.8 support
- https://lists.openstack.org/archives/list/openstack-discuss@li>

Change-Id: Ia1e92968d88f64b78e8adc4a747bb0377251712d

releasenotes/notes/drop-python38-support-f95c4ad6ba695aea.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 3.8 support has been dropped. Last release of
+    venus-temepst-plugin to support python 3.8 is 3.3.0.
+    The minimum version of Python now supported is Python 3.9.

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = http://www.openstack.org/
-python_requires = >=3.8
+python_requires = >=3.9
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -17,8 +17,10 @@ classifier =
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: 3 :: Only
     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
 
 keywords =
     setup