Update setup.cfg as suggested by @henryiii

Author: rwgk

setup.cfg

@@ -14,7 +14,6 @@ classifiers =
     Topic :: Utilities
     Programming Language :: C++
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
@@ -39,5 +38,5 @@ project_urls =
     Chat = https://gitter.im/pybind/Lobby
 
 [options]
-python_requires = >=3.6
+python_requires = >=3.7
 zip_safe = False