Update needed for Rust v1.77.1

error: field `0` is never read
  --> hardware/interfaces/security/keymint/aidl/default/main.rs:38:24
   |
38 | 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
   |
38 | struct HalServiceError(());
   |                        ~~

error: aborting due to 1 previous err


Bug: http://b/330185853
Test: ./test_compiler.py --prebuilt-path dist/rust-dev.tar.xz  --target aosp_cf_x86_64_phone --image
Change-Id: I57f3bd1d702c97929f5fd34f909aa72aa2f2ba02