Update python classifier in setup.cfg

As per the current release tested runtime, we test
till python 3.11 so updating the same in python
classifier in setup.cfg

Change-Id: I45b783687458e19b3baafadf197e5506108a97fc

Author: Ghanshyam Mann

setup.cfg

@@ -6,6 +6,7 @@ description_file =
 author = OpenStack
 author_email = [email protected]
 home_page = https://docs.openstack.org/cloudkitty-dashboard/latest/
+python_requires = >=3.8
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -14,10 +15,10 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
-    Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
+    Programming Language :: Python :: 3.11
 
 [files]
 packages =