Fix clippy lints for Bluetooth for 1.79.0 update

```
error: field `btif_avrcp` is never read
  --> packages/modules/Bluetooth/system/gd/rust/topshim/facade/src/media_service.rs:37:9
   |
32 | pub struct MediaServiceImpl {
   |            ---------------- field in this struct
...
37 |     pub btif_avrcp: Arc<Mutex<Avrcp>>,
   |         ^^^^^^^^^^
   |
   = note: `MediaServiceImpl` has a derived impl for the trait `Clone`, but this is intentionally ignored during dead code analysis
   = note: `-D dead-code` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(dead_code)]`
```

Bug: http://b/346588808
Bug: 346588808
Test: ./toolchain/android_rust/tools/test_compiler.py --target aosp_cf_x86_64_phone --all-rust --reuse-prebuilt
Test: m (with new toolchain)
Change-Id: I8c1d4e64b1bac21f49a69dfe6ae4be321ae09ca0