build fix (#339)

Author: RushabhBhansali

src/Microsoft.ComponentDetection.Detectors/rust/Contracts/CargoPackage.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.Serialization;
 
 namespace Microsoft.ComponentDetection.Detectors.Rust.Contracts