Revert D34503882: Support CSR to COO conversion in to_sparse.
Test Plan: revert-hammer
Differential Revision:
D34503882 (https://github.com/pytorch/pytorch/commit/84f4e9c10a40a0ee3f94059c722baf5ceb5f181e)
Original commit changeset: 4a781647a0ae
Original Phabricator Diff: D34503882 (https://github.com/pytorch/pytorch/commit/84f4e9c10a40a0ee3f94059c722baf5ceb5f181e)
fbshipit-source-id: cf161171a3b51aa3c0f2b15501956873b1ba29dd
(cherry picked from commit 924c19071713777700087087b27b388eb057d8d9)
