Remove redundant "build" setup.py commond from onnx scripts

Summary: Pull Request resolved: pytorch#16487

Differential Revision: D13858628

Pulled By: bddppq

fbshipit-source-id: e1ff3fc5f9be5d3dbbf96ee73c3a8c901b440b82

Author: bddppq

scripts/onnx/install-develop.sh

@@ -15,4 +15,4 @@ pip install -e "$tp2_dir/onnx"
 # Install caffe2 and pytorch
 pip install -r "$top_dir/caffe2/requirements.txt"
 pip install -r "$top_dir/requirements.txt"
-python setup.py build develop
+python setup.py develop