Revert "Expose `FaceManager` APIs as `@SystemApi`."

Revert submission 25750009-facemanager_20240110

Reason for revert: Project cancelled.

Reverted changes: /q/submissionid:25750009-facemanager_20240110

Test: Local
Change-Id: I7e329f311b3eb599195f415cf39dc28bb11139a1
12 files changed