MINOR: quic: do not reject PADDING followed by other frames

It is valid for a QUIC packet to contain a PADDING frame followed by
one or several other frames.

quic_parse_padding_frame() does not require change as it detect properly
the end of the frame with the first non-null byte.

This allow to use quic-go implementation which uses a PADDING-CRYPTO as
the first handshake packet.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index a132082..19c6958 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -1998,10 +1998,6 @@
 
 		switch (frm.type) {
 		case QUIC_FT_PADDING:
-			if (pos != end) {
-				TRACE_DEVEL("wrong frame", QUIC_EV_CONN_PRSHPKT, ctx->conn, pkt);
-				goto err;
-			}
 			break;
 		case QUIC_FT_PING:
 			break;