Fix casting issue

Author: jcheng

Microsoft.SystemForCrossDomainIdentityManagement/Schemas/TrustedJsonFactory.cs

@@ -12,8 +12,7 @@ public class TrustedJsonFactory : JsonFactory
         public override Dictionary<string, object> Create(string json)
         {
             Dictionary<string, object> result =
-                (Dictionary<string, object>)JsonConvert.DeserializeObject(
-                    json);
+                JsonConvert.DeserializeObject<Dictionary<string, object>>(json);
             return result;
         }