MINOR: mux-quic: complete trace when stream is not found

Display the ID of the stream not found. This will help to detect when we
received retransmitted frames for an already closed stream.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 9dc4c40..fa0207e 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -197,7 +197,7 @@
 
 	strm_node = qcc_get_qcs(qcc, id);
 	if (!strm_node) {
-		fprintf(stderr, "%s: stream not found\n", __func__);
+		fprintf(stderr, "%s: stream not found: %ld\n", __func__, id);
 		return 1;
 	}