Update documentation for CTCLoss (#20422)
Summary:
Change `Inputs` to `Shape` to unify the format of CTCLoss `class`, and add the type of `Output` in `Shape`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20422
Differential Revision: D15393484
Pulled By: ezyang
fbshipit-source-id: 5b49647f9740de77db49a566fa2de74fcecd9110