Drop python 3.9 and support python 3.13

Due to requirements repo dropped the constraints for
python3.9[1], Tempest needs to drop the python 3.9
support[2]. Because Tempest master cannot support
py3.9 anymore, it needs to be dropped from tempest
plugins also.

Also, add python 3.13 support which is tested as mandatory
in 2026.2 cycle.

[1] https://review.opendev.org/c/openstack/requirements/+/957587
[2] https://review.opendev.org/c/openstack/tempest/+/966101

Change-Id: I9586938ab1e9012f72bd3d2240c9aacae04499a1
Signed-off-by: Ghanshyam Maan <gmaan@ghanshyammann.com>

setup.cfg

@@ -6,7 +6,7 @@ description-file =
 author = OpenStack
 author-email = openstack-discuss@lists.openstack.org
 home-page = https://docs.openstack.org/keystone/latest/
-python_requires = >=3.9
+python_requires = >=3.10
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,10 +15,10 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
 
 [files]
 packages =