Adding import namespace

Author: gnongsie

cybersource-rest-auth-netstandard/AuthenticationSdk/AuthenticationSdk/util/JWEUtility.cs

@@ -3,6 +3,7 @@
 using Org.BouncyCastle.Crypto.Parameters;
 using Org.BouncyCastle.OpenSsl;
 using Org.BouncyCastle.Security;
+using System;
 using System.IO;
 using System.Security.Cryptography;
 using AuthenticationSdk.core;