BUG/MINOR: quic: increment pos pointer on QMux transport params parsing

QUIC frame parsers functions take a <pos> pointer as input argument for
the data to be parsed. If parsing is successful, <pos> must be
incremented to point to the next data.

Increment was not performed when parsing QMux transport parameters
frame. This commit fixes this. Note that for now there is no real issue
as xprt_qstrm does not check the QMux frame length.

No need to backport.

src/quic_frame.c

@@ -1081,6 +1081,7 @@ static int quic_parse_qmux_transport_parameters(struct quic_frame *frm, struct q
 	if (!quic_transport_params_decode(&params_frm->params, 1, *pos, end))
 		return 0;
 
+	*pos += len;
 	return 1;
 }