Remove Python 2 support from packaging

(This is included in the v8.0 distribution)

setup.cfg

@@ -2,4 +2,3 @@
 license_file = LICENSE
 
 [bdist_wheel]
-universal=1

setup.py

@@ -43,6 +43,7 @@ setup(
     license="BSD License",
     packages=["anymail"],
     zip_safe=False,
+    python_requires='>=3.5',
     install_requires=["django>=2.0", "requests>=2.4.3"],
     extras_require={
         # This can be used if particular backends have unique dependencies.