Fix exception message for fallback SOCKS5 error.

Fixes issue #167.

src/Renci.SshNet/Session.cs

@@ -2087,7 +2087,7 @@ private void ConnectSocks5()
                 case 0x08:
                     throw new ProxyException("SOCKS5: Address type not supported.");
                 default:
-                    throw new ProxyException("SOCKS4: Not valid response.");
+                    throw new ProxyException("SOCKS5: Not valid response.");
             }
 
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