add missing line from using block

Emby.Server.Implementations/Updates/InstallationManager.cs

@@ -19,6 +19,7 @@ using MediaBrowser.Common.Updates;
 using MediaBrowser.Controller.Configuration;
 using MediaBrowser.Model.Events;
 using MediaBrowser.Model.IO;
+using MediaBrowser.Model.Net;
 using MediaBrowser.Model.Serialization;
 using MediaBrowser.Model.Updates;
 using Microsoft.Extensions.Configuration;