Remove reference to setuptools.command.test.test

Originally skbuild supplied its own test command which called "develop"
before calling original setuptools test command.

In order to avoid calling "develop", we directly exchanged this
skbuild.test command with setuptools.command.test.test
(It is though unclear if test command from setuptools was ever called by
any parts of our solution.)

Note that in setup.py we only imported setuptools, not its submodules
like setuptools.command.test. However setuptools.command.test was
imported directly in the skbuild, where they exchanged 'test' with their
own command. So we happened to use it indirectly.

In 0.18 release skbuild removed custom test command in [1].
As setuptools.command.test import went along with it, we started
getting errors like
module 'setuptools.command' has no attribute 'test'

As test command is supposed to be deprecated and reason for our own
override in setup.py is gone, we just drop the line altogether.

[1]scikit-build/scikit-build@dde5e79

python/setup.py

@@ -2,7 +2,6 @@
 
 import os
 import skbuild
-import setuptools
 
 class get_pybind_include(object):
     def __init__(self, user=False):
@@ -54,7 +53,4 @@ def get_long_description():
         # supported OS X release 10.9
         '-DCMAKE_OSX_DEPLOYMENT_TARGET=10.9',
     ],
-    # skbuild's test imples develop, which is pretty obnoxious instead, use a
-    # manually integrated pytest.
-    cmdclass = { 'test': setuptools.command.test.test },
 )