Merge "docs: Update READ_EXTERNAL_STORAGE explanation" into tm-dev am: 19a290e320 am: 117f42954d

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20066630

Change-Id: I71b22e628490a4c5f67a22ac1139371647ccebd7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>