[BE] Remove outdated RPC benchmark (pytorch#146716)

We have lots of outdated unused + uncalled code in our codebase, namely in our benchmarks and examples folders among others. The last change to this directory was 4 years ago and this code looks dead. cc @albanD @H-Huang for feedback

Pull Request resolved: pytorch#146716
Approved by: https://github.com/Skylion007, https://github.com/H-Huang

Author: janeyx99