Migrate to cargo_embargo. am: 95be593d39

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-macro/+/2824494

Change-Id: Ie5af664d4bd1f9fe4eb86eb1fe06f19dfe9ddb05
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>