remove non-onnx caffe2 builds (#29478)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29478
caffe2 is still tested internally, but removing the OSS configurations.
ONNX remains, however. I will look at migrating them to the pytorch
docker images so we can kill the entire caffe2 part of the config
Test Plan: Imported from OSS
Differential Revision: D18406233
Pulled By: suo
fbshipit-source-id: c3a7d1c58a2828f04778497faa1b5d13b67acbbb
