Disallow system apps to be installed/updated as instant. am: c61ee9f4

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/25715852



Change-Id: I52bba4e453e785ea9f9030c2beffd42481f09123
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>