Revert D35511873: [iOS][coreml] Add CoreML memory observer
Test Plan: revert-hammer
Differential Revision:
D35511873 (https://github.com/pytorch/pytorch/commit/22fb929405b292c5d9ccfea30b2077dee1737912)
Original commit changeset: 59f2fa2d0211
Original Phabricator Diff: D35511873 (https://github.com/pytorch/pytorch/commit/22fb929405b292c5d9ccfea30b2077dee1737912)
fbshipit-source-id: be83517fee4ac58e6ca4f126cba7b088625ddd1f
(cherry picked from commit 448e9c8794dc9bd77442583eefeef2d6cb2a5308)
