system/rust: Update Cargo.toml

- remove unused dependency grpcio
- bump pdl-compiler to 0.3.0
- bump pdl-runtime to 0.3.0
- bump bitflags to 2.5.0

Bug: 331817295
Test: m com.android.btservices
Test: cd system/rust && cargo build
Flag: EXEMPT, build change
Change-Id: I8adeae054f00350c917e353bce00414ab6f138a9