remove _deprecated_global_ns (#1224)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/1224

This is a reland of https://github.com/pytorch/pytorch/issues/112757. Cannot land original one internally because internal diff is not in sync with OSS due to issues in dealing with two export repos (executorch and pytorch) using the ghimport-ghexport approach.

Will try the web UI of import and export instead of ghimport and ghexport flow.

cc avikchaudhuri gmagogsfm zhxchen17 tugsbayasgalan angelayi suo

X-link: https://github.com/pytorch/pytorch/pull/113813

Reviewed By: angelayi

Differential Revision: D51373556

Pulled By: ydwu4

fbshipit-source-id: 3e73f2a357e6ab4d5db0d59e7c09eb20eaf72602