Remove python3.9 support

Based on [0] python 3.9 will go EOL before 2025.2 release.

[0] https://review.opendev.org/c/openstack/governance/+/941141

Change-Id: I867ebda0dc133d24da068ca6028a777be8804a6c
diff --git a/setup.cfg b/setup.cfg
index 6070e2a..bc52823 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -6,7 +6,7 @@
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/designate-tempest-plugin/latest/
-python_requires = >=3.9
+python_requires = >=3.10
 classifier =
     Environment :: OpenStack
     Environment :: No Input/Output (Daemon)
@@ -18,7 +18,6 @@
     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