Document fix for issue 2010.

Renci.SshClient/Build/nuget/SSH.NET.nuspec

@@ -37,6 +37,7 @@
           * NullReferenceException when SftpFileStream is finalized after dispose of session (issue #2013)
           * BlockCipher.Encrypt fails if input message is not padded (issue #2547)
           * ScpClient: Missing files when using DirectoryUpload (issue #1382)
+          * Dynamic port forwarding slows down to a crawl (issue #2010)
 
           2014.4.6-beta1
           ==============