Use cpu docker image for cpu builds (#60920)
Summary:
This was set to use the [CUDA 10.0 image](https://hub.docker.com/r/pytorch/manylinux-cuda100) which hasn't been updated in quite a while, so fix it to use the up-to-date [cpu image](https://hub.docker.com/r/pytorch/manylinux-cpu) instead
Pull Request resolved: https://github.com/pytorch/pytorch/pull/60920
Reviewed By: janeyx99
Differential Revision: D29447897
Pulled By: driazati
fbshipit-source-id: 6e89091110361d0ddda859bb266e229c6cf83c2d
