remove redundant xmppRestartStream from DigestMD5

source/Network/Xmpp/Sasl/Mechanisms/DigestMd5.hs

@@ -63,7 +63,6 @@ xmppDigestMd5 authcid authzid password = do
         cnonce <- liftIO $ makeNonce
         _b <- respond . Just $ createResponse hostname pairs cnonce
         challenge2 <- pullFinalMessage
-        _ <- ErrorT $ left AuthStreamError <$> xmppRestartStream
         return ()
       where
         -- Produce the response to the challenge.
@@ -137,4 +136,4 @@ digestMd5 :: Text -- ^ Authentication identity (authcid or username)
           -> SaslHandler
 digestMd5 authcid authzid password = ( "DIGEST-MD5"
                                      , xmppDigestMd5 authcid authzid password
-                                     )
+                                     )