Remove Python 3.8 and 3.9 support

Python 3.8 was removed from the tested runtimes for 2024.2 and has
not been tested since then.

Change-Id: I9beed8d8153e4faf51f4c0446750eaccb40a9582

Author: anfimovir

releasenotes/notes/drop-python-38-and-39.yaml

@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    Support for Python 3.8 and 3.9 has been dropped.

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = [email protected]
 home_page = https://docs.openstack.org/cloudkitty-dashboard/latest/
-python_requires = >=3.8
+python_requires = >=3.10
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -15,14 +15,16 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.8
-    Programming Language :: Python :: 3.9
+    Programming Language :: Python :: Implementation :: CPython
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
+    Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
 
 [files]
 packages =
     cloudkittydashboard
 
 [upload_sphinx]
-upload-dir = doc/build/html
+upload_dir = doc/build/html