setup.py: Update classifiers

Author: Synss

setup.py

@@ -198,10 +198,10 @@ def readme():
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Programming Language :: Cython",
-        "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",
         "License :: OSI Approved :: MIT License",
         "Topic :: Security :: Cryptography",
     ],