Merge "docs: Clarify when certificate is self-signed" into main am: 69bbd1c8 am: 76ee8400

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2779947



Change-Id: Ie7e0bbd8f927dbed233a21dd4426c66454782896
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>