Fix issues introduced from cherry-picking

Author: alerickson

src/code/ServerApiCall.cs

@@ -10,7 +10,6 @@
 using System.Text;
 using System.Runtime.ExceptionServices;
 using System.Management.Automation;
-using System;
 
 namespace Microsoft.PowerShell.PSResourceGet.Cmdlets
 {

src/code/Utils.cs

@@ -13,6 +13,7 @@
 using System.Management.Automation.Language;
 using System.Management.Automation.Runspaces;
 using System.Runtime.InteropServices;
+using System.Security;
 using Microsoft.PowerShell.Commands;
 using Microsoft.PowerShell.PSResourceGet.Cmdlets;
 using System.Net.Http;