[automerge] Fix exposing private messages files through attachments with a content URI. 2p: 0d5452146c 2p: 471c3e9320 am: 749732f47b am: 78c26722e2 am: 7bf7a451f7

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Messaging/+/23089831

Change-Id: Ic13449a3884c39331cd66ab3733d0f97d8ae9de8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>