[automerger skipped] Merge "Disable updatable system manifest for T" into tm-dev am: 4b9437eb -s ours

am skip reason: Merged-In I6b890e5536c17dd53722e2c3a781c85dd9d6bdf0 with SHA-1 87d1af1d is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16968723

Change-Id: I1e30db369e265f379593a103354cdfb5c7485ddf