remove duplicate autograd srcs (#46059)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/46059
These files are not generated sources, and they also already exist in another variable in the same file (`libtorch_extra_sources`).
Test Plan: CI green
Reviewed By: malfet
Differential Revision: D24203450
fbshipit-source-id: 0c9e12cd1a292c5484961876d4fa7f2341a3165b
