Update src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs

Co-authored-by: Peter Ombwa <peombwa@microsoft.com>

Author: timayabi2020

src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs

@@ -20,7 +20,6 @@
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
-using System.Web;
 using static Microsoft.Graph.PowerShell.Authentication.Helpers.AsyncHelpers;
 using DriveNotFoundException = System.Management.Automation.DriveNotFoundException;