Use #![register_tool] instead of #![register_attr]

CC https://github.com/rust-lang/rust/issues/66079

components/dom_struct/lib.rs

@@ -17,7 +17,7 @@ pub fn dom_struct(args: TokenStream, input: TokenStream) -> TokenStream {
     }
     let attributes = quote! {
         #[derive(DenyPublicFields, DomObject, JSTraceable, MallocSizeOf)]
-        #[must_root]
+        #[unrooted_must_root_lint::must_root]
         #[repr(C)]
     };