Remove Python 3.6/7 support again

... with a release note added.

Change-Id: I4cec8d2e9664962b5abd7ac9bfd7b7a3bd419f61

releasenotes/notes/remove-py36-37-b4292e584fe8ead5.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Python 3.6 and 3.7 are no longer supported. The minimum python version
+    currently supported is 3.8.

setup.cfg

@@ -6,7 +6,7 @@ description_file =
 author = OpenStack
 author_email = openstack-discuss@lists.openstack.org
 home_page = http://yaql.readthedocs.io
-python_requires = >=3.6
+python_requires = >=3.8
 classifier =
     Environment :: OpenStack
     Intended Audience :: Information Technology
@@ -17,8 +17,6 @@ classifier =
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: 3 :: Only
     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