Revert "[rust] allow unused-macro-rules to unblock toolchain roll"

This reverts commit 5909ed0.

Reason for revert: lint is allow-by-default after rust-lang/rust#97032

Original change's description:
> [rust] allow unused-macro-rules to unblock toolchain roll
>
> Bug: 100318
> Change-Id: Ided9428282c66e63cda934a5f456223750703179
> Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/679506
> Reviewed-by: Joseph Ryan <josephry@google.com>
> Fuchsia-Auto-Submit: Dan Johnson <computerdruid@google.com>
> Reviewed-by: Tyler Mandry <tmandry@google.com>
> Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>

Bug: 100318
Change-Id: I2ebf0b0e9c9e28d8a2588fc92dfe7428c77ca4cf
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/679988
Reviewed-by: RubberStamper 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Dan Johnson <computerdruid@google.com>
Reviewed-by: Joseph Ryan <josephry@google.com>

Author: ComputerDruid

src/lib/storage/vfs/rust/src/path.rs

@@ -182,8 +182,6 @@ impl AsRef<str> for Path {
 mod tests {
     use super::*;
 
-    #[allow(unknown_lints)] // TODO(fxbug.dev/99424): remove this after toolchain roll when lint is known
-    #[allow(unused_macro_rules)] // TODO(fxbug.dev/100318): remove unused macro rules and re-enable
     macro_rules! simple_construction_test {
         (path: $str:expr, $path:ident => $body:block) => {
             match Path::validate_and_split($str) {