remove superfluous check for large packets

as we're already doing the correct check further down anyway there's no point
in doing the (wrong) check further up as well. Paul Veldkamp pointed this out.

src/transport.c

@@ -431,7 +431,7 @@ _libssh2_transport_read(LIBSSH2_SESSION * session)
              * and we can extract packet and padding length from it
              */
             p->packet_length = _libssh2_ntohu32(block);
-            if ((p->packet_length < 1) || (p->packet_length > PACKETBUFSIZE))
+            if (p->packet_length < 1)
                 return PACKET_FAIL;
 
             p->padding_length = block[4];