Merge "Update documentation regarding auth-bound keys." am: f854451558 am: b4a708506a am: 70949fe837

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2633330

Change-Id: I9f7cb5f9a8e9bb7507b3bf1803bfd8c697c08124
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>