Adding @hide to UpdateEngineStable am: 4914ffd6b2 am: 8ccfd25204 am: 4213083427

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2893923

Change-Id: I267efb56acf6f0d04aa0cfa38949677b7699ee54
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>