Replaced HttpStatusCode.PermanentRedirect with 308 for compatibility with .NET Standard 2.0

Author: TalAloni

StandardSocketsHttpHandler/Net/Http/SocketsHttpHandler/RedirectHandler.cs

@@ -81,7 +81,7 @@ private Uri GetUriForRedirect(Uri requestUri, HttpResponseMessage response)
                 case HttpStatusCode.SeeOther:
                 case HttpStatusCode.TemporaryRedirect:
                 case HttpStatusCode.MultipleChoices:
-                case HttpStatusCode.PermanentRedirect:
+                case (HttpStatusCode)308: // HttpStatusCode.PermanentRedirect
                     break;
 
                 default: