Drop support for Python 3.9

in release notes add information about remove support for Python 3.8 too.

Change-Id: I25909b788d8f724ce963e622c7a3924af662e13b

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

@@ -1,12 +1,12 @@
 [metadata]
 name = mistral-dashboard
 summary = Mistral dashboard
-description_file = README.rst
+description_file =
+    README.rst
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = https://docs.openstack.org/mistral/latest/
-license = Apache License, Version 2.0
-python_requires = >=3.9
+python_requires = >=3.10
 classifiers =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -17,10 +17,10 @@ classifiers =
     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
+    Programming Language :: Python :: 3.13
 
 [global]
 setup_hooks =