stop supporting Python2

Author: tenzen-y

sdk/python/v1beta1/setup.py

@@ -35,9 +35,8 @@
         'Intended Audience :: Developers',
         'Intended Audience :: Education',
         'Intended Audience :: Science/Research',
-        'Programming Language :: Python :: 2',
-        'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
+        "Programming Language :: Python :: 3 :: Only",
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',