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

Co-Authored-By: Ghanshyam Maan <gmaan@ghanshyammann.com>
Change-Id: I48c74394ed1993c90452fb852b524507ea78a2ed
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>
diff --git a/setup.cfg b/setup.cfg
index e06cda0..a83b4b8 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -5,7 +5,7 @@
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 url = http://www.openstack.org/
-python_requires = >=3.9
+python_requires = >=3.10
 classifiers =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,10 +15,10 @@
     Programming Language :: Python
     Programming Language :: Python :: 3 :: Only
     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 =