Migrate to cargo_embargo. am: f23ad98f7e

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/pest_generator/+/2821939

Change-Id: Iee77ae47c8d4b7b497f9fc59f0bea623182ed12b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>