Enable lint again after update to  Rust v1.77.1

Test: Build and run
Bug: 333894983
Change-Id: Iae60819c9345b44f716183d746454a35f190b9e2
diff --git a/libs/gui/rust/aidl_types/src/lib.rs b/libs/gui/rust/aidl_types/src/lib.rs
index 4e86ed6..fead018 100644
--- a/libs/gui/rust/aidl_types/src/lib.rs
+++ b/libs/gui/rust/aidl_types/src/lib.rs
@@ -20,13 +20,11 @@
     StatusCode,
 };
 
-#[allow(dead_code)]
 macro_rules! stub_unstructured_parcelable {
     ($name:ident) => {
         /// Unimplemented stub parcelable.
-        #[allow(dead_code)]
         #[derive(Debug, Default)]
-        pub struct $name(Option<()>);
+        pub struct $name(());
 
         impl UnstructuredParcelable for $name {
             fn write_to_parcel(&self, _parcel: &mut BorrowedParcel) -> Result<(), StatusCode> {