Avoid bdist_wheel.universal deprecation warning. Refs #1675

See:
pypa/setuptools#4617
pypa/setuptools#4939

Author: mnaberez

setup.cfg

@@ -1,5 +1,12 @@
 [easy_install]
 zip_ok = false
 
+;Marking a wheel as universal with "universal = 1" was deprecated
+;in Setuptools 75.1.0.  Setting "python_tag = py2.py3" should do
+;the equivalent on Setuptools 30.3.0 or later.
+;
+;https://github.com/pypa/setuptools/pull/4617
+;https://github.com/pypa/setuptools/pull/4939
+;
 [bdist_wheel]
-universal = 1
+python_tag = py2.py3