exception message fix

Author: honfika

src/Titanium.Web.Proxy/EventArguments/LimitedStream.cs

@@ -63,7 +63,7 @@ private void getNextChunk()
 
             if (!int.TryParse(chunkHead, NumberStyles.HexNumber, null, out int chunkSize))
             {
-                throw new ProxyHttpException($"Invalid chunk length: '{chunkSize}'", null, null);
+                throw new ProxyHttpException($"Invalid chunk length: '{chunkHead}'", null, null);
             }
 
             bytesRemaining = chunkSize;