Merge "Disallow system apps to be installed/updated as instant." into udc-dev...

Merge "Disallow system apps to be installed/updated as instant." into udc-dev am: 4c390bd2 am: 0ddf73b8

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/25715830



Change-Id: I89ed13182c7f4eeb5472e678858bcf7b1ee0ee6d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>