Remote dead code

Pull Request resolved: #432

Not sure why these files never got deleted when I removed _monarch. There are no longer any imports of monarch._monarch in the codebase.
ghstack-source-id: 294607622
@exported-using-ghexport

Differential Revision: [D77771097](https://our.internmc.facebook.com/intern/diff/D77771097/)

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Author: zdevito