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@lists.openstack.org/thread/FOWV4UQZTH4DPDA67QDEROAESYU5Z3LE/

Change-Id: Ia27257e0ab90979c59c479c2ddf946e926c1aed3
diff --git a/releasenotes/notes/drop-python38-support-07c1fab194bad54a.yaml b/releasenotes/notes/drop-python38-support-07c1fab194bad54a.yaml
new file mode 100644
index 0000000..70f3814
--- /dev/null
+++ b/releasenotes/notes/drop-python38-support-07c1fab194bad54a.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Python 3.8 support has been dropped. Last release of
+    manila-tempest-plugin to support python 3.8 is 2.5.0.
+    The minimum version of Python now supported is Python 3.9.