Update needed for Rust v1.77.0

error: field `0` is never read
  --> system/core/trusty/keymint/src/keymint_hal_main.rs:40:24
   |
40 | struct HalServiceError(String);
   |        --------------- ^^^^^^
   |        |
   |        field in this struct
   |
   = note: `HalServiceError` has derived impls for the traits `Clone` and `Debug`, but these are intentionally ignored during dead code analysis
   = note: `-D dead-code` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(dead_code)]`
help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
   |
40 | struct HalServiceError(());
   |                        ~~


Bug: http://b/330185853
Test: ./test_compiler.py --prebuilt-path dist/rust-dev.tar.xz  --target aosp_cf_x86_64_phone --image

Change-Id: I79fb9019ba00900508aead414de80edd51f3fa2e