CLEANUP: quic: No more use ->rx_list MT_LIST entry point (quic_rx_packet)

This quic_rx_packet is definitively no more used.

Should be backported to 2.6 to ease the future backports.
diff --git a/include/haproxy/xprt_quic-t.h b/include/haproxy/xprt_quic-t.h
index 39280b8..6ee7f42 100644
--- a/include/haproxy/xprt_quic-t.h
+++ b/include/haproxy/xprt_quic-t.h
@@ -391,7 +391,6 @@
 
 struct quic_rx_packet {
 	struct list list;
-	struct mt_list rx_list;
 	struct list qc_rx_pkt_list;
 	struct quic_conn *qc;
 	unsigned char type;