Migrate to cargo_embargo. am: 81325be9a8 am: 56480aaddb

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/unicode-ident/+/2828192

Change-Id: I4e2a9f77c5d65767ccdebfa219170924af54d3ba
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>