Fix wrong changes from #54103 (#54610)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54610
The `.is_view()` method actually only refers to backward mode views
This is not a problem right now in master (and thus I didn't revert the other PR) because nothing creates forward AD views.
Test Plan: Imported from OSS
Reviewed By: gchanan
Differential Revision: D27396756
Pulled By: albanD
fbshipit-source-id: 64ff11c6f2486c6430714988d1cf6ecf3d80dccb
