Use expect to fill in pytorchbot token (#20459)
Summary:
In this PR, we use `expect` to fill in the token for pytorchbot when doing `git push`, so that we don't need to save the token in the git remote URL.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20459
Differential Revision: D15811676
Pulled By: yf225
fbshipit-source-id: cd3b780da05d202305f76878e55c3435590f15a8
