Migrate to cargo_embargo. am: 66e61af4a9

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/litrs/+/2796436

Change-Id: Ic020b42677107bc94e335d90ff5fbead48ae0e7a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>