Don't set Content-Length, it doesn't play well with IIS

Middleware such as dynamic compression or IIS HTTP/2 implementations can interact badly with a pre-set content-length. It's not worth it.

core/NewModuleHelpers.cs

@@ -48,11 +48,6 @@ internal static string GetContentTypeFromBytes(byte[] data)
         /// <exception cref="InvalidOperationException"></exception>
         internal static async Task ProxyToStream(Stream sourceStream, HttpResponse response)
         {
-            if (sourceStream.CanSeek)
-            {
-                var contentLength = sourceStream.Length - sourceStream.Position;
-                if (contentLength > 0) response.Headers.Add("Content-Length", contentLength.ToString());
-            }
 
             // We really only need 12 bytes but it would be a waste to only read that many. 
             const int bufferSize = 4096;
@@ -340,4 +335,4 @@ public async Task ProcessWithStreamCache(ILogger logger, IStreamCache streamCach
         // }
 
     }
-}
+}