replace LegacyTracedModule with torchscript used in add_graph (#21339)
Summary:
The new implementation of tracing supports more module. So many error-handling code can be removed by placing the old one (LegacyTracedModule).
cc orionr
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21339
Reviewed By: natalialunova
Differential Revision: D15695154
Pulled By: orionr
fbshipit-source-id: af7d35754e9f34bd1a0ad7b72a9ebe276ff8ab98
