Migrate to cargo_embargo. am: 7994f86262

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/protobuf/+/2856056

Change-Id: I2dbbe3b6225c4b10646c7b1497b9dfc67d4af0a2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>