Remove CoreMLMemoryObserver (#83703)
Summary: We added this observer to help us diagnose memory issues that have since resolved. It should be safe to clean this up.
Test Plan: Diff just removed logging, so just build IG and confirm no errors.
Differential Revision: D38843701
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83703
Approved by: https://github.com/mcr229
