Migrate to cargo_embargo. am: 34065597a2

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rustc-demangle-capi/+/2832426

Change-Id: I7547400815b341e56cfb44dba3896f458267b858
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>