Kill ConvTransposeMixin.forward, which doesn't seem to be used. (#25326)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25326
And also uses self._backend, which I'm trying to kill or at least drastically reduce.
Test Plan: Imported from OSS
Differential Revision: D17097303
Pulled By: gchanan
fbshipit-source-id: f55d7df2a668425978499d4a4338b23ba6cf1b90
