remove SkipInputShape flag (#29615)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29615
Remove that flag as it's not needed any more.
Test Plan: na
Reviewed By: hl475
Differential Revision: D18440271
fbshipit-source-id: 41b0659c72ef746a1cc268174fd1e7dc2beb1ae2
