Remove requires from setup.py

- Also remove comment that was probably pointing out duplicate requires
diff --git a/setup.py b/setup.py
index 7f4b86b..78e66ea 100644
--- a/setup.py
+++ b/setup.py
@@ -63,9 +63,8 @@
       python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*",
       package_data={"dateutil.zoneinfo": ["dateutil-zoneinfo.tar.gz"]},
       zip_safe=True,
-      requires=["six"],
       setup_requires=['setuptools_scm'],
-      install_requires=["six >=1.5"],  # XXX fix when packaging is sane again
+      install_requires=["six >=1.5"],
       classifiers=[
           'Development Status :: 5 - Production/Stable',
           'Intended Audience :: Developers',