Remove py39 reference from setup.cfg

Change-Id: I80ebf4800cc73c5315940e5d965a7612711e1d21

releasenotes/notes/drop-py39-a9a5f0b7addc2f12.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    Python 3.9 support has been dropped. The last release of neutron-dynamic-routing
+    to support py39 is Openstack 2025.1 (Epoxy).
+    For details about supported runtimes in Openstack 2025.2 please check:
+    https://governance.openstack.org/tc/reference/runtimes/2025.2.html

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/neutron-dynamic-routing/latest/
-python_requires = >=3.9
+python_requires = >=3.10
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -17,7 +17,6 @@ classifier =
     Programming Language :: Python :: Implementation :: CPython
     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