update_engine: update help text am: 96eb042527 am: 5cd102e2ac

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2959226

Change-Id: Id1fc42eea0f24a9ecf19b725bc1a1ebc064d997b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>