[cr133][Rust] unused imports.

error: unused import: `Hashable`
 --> ../../brave/components/brave_wallet/browser/zcash/rust/librustzcash/src/zcash_primitives/src\merkle_tree.rs:7:14
  |
7 |     Address, Hashable, Level, MerklePath, Position,
  |              ^^^^^^^^
  |
  = note: `-D unused-imports` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(unused_imports)]`

error: unused import: `Write`
 --> ../../brave/components/brave_wallet/browser/zcash/rust/librustzcash/src/zcash_primitives/src\transaction\mod.rs:4:27
  |
4 | use std::io::{self, Read, Write};
  |                           ^^^^^

Chromium change:

https://chromium.googlesource.com/chromium/src/+/6f81efe9a3d000dcbc952d6f14284c8178a960ec

commit 6f81efe9a3d000dcbc952d6f14284c8178a960ec
Author: Lukasz Anforowicz <lukasza@chromium.org>
Date:   Thu Jan 2 13:45:03 2025 -0800

    Stop globally disabling `unused-imports` lint when compiling Rust.

    rust-lang/rust#121708 (comment)
    points out that new linting scenarios have been moved into a separate
    lint.  Thanks to this, we no longer need to globally disable this lint
    in Chromium (some narrower exclusions still need to apply).

    Bug: chromium:326247202

components/brave_wallet/browser/zcash/rust/librustzcash/BUILD.gn

@@ -56,6 +56,10 @@ rust_static_library("zcash_primitives") {
     "src/zcash_primitives/src/transaction/components/orchard.rs",
     "src/zcash_primitives/src/transaction/mod.rs",
   ]
+
+  # TODO(cypt4): Fix unused imports and remove this flag.
+
+  rustflags = [ "-Aunused-imports" ]
   deps = [
     ":zcash_encoding",
     ":zcash_protocol",