remove uses of std::shared_ptr<Module> (#21934)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21934
ghimport-source-id: e64ab9096f43749ead3ac5567675b815da295664
Test Plan: Imported from OSS
Differential Revision: D15892401
Pulled By: zdevito
fbshipit-source-id: 6424139206593ff944556c69d8a54723884eacaf
