Merge "docs: Update WRITE_EXTERNAL_STORAGE explanation" into tm-dev am: d13571c3 am: 1590df85

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20136895



Change-Id: I8cb49b83d0eeddcfea7e566693780bdf842a3f54
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>