remove six dependency install (#1792)

Author: edgarriba

packaging/build_wheel.sh

@@ -8,8 +8,6 @@ export BUILD_TYPE=wheel
 setup_env 0.6.0
 setup_wheel_python
 pip_install numpy pyyaml future ninja
-# TODO remove after https://github.com/pytorch/pytorch/pull/27282 gets merged
-pip_install six
 setup_pip_pytorch_version
 python setup.py clean
 IS_WHEEL=1 python setup.py bdist_wheel