Remove deprecated fields from update_metadata protobuf am: 9ae7dc6045

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2056748

Change-Id: I297406b19d6163e2271232acea3bdb5fe065c684
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>