CLEANUP: quic: remove unused scid_node

Remove unused scid_node member for quic_conn structure. It was prepared
for QUIC backend support.

This should be backported up to 2.7.
diff --git a/include/haproxy/quic_conn-t.h b/include/haproxy/quic_conn-t.h
index 2213a7f..1efb8f9 100644
--- a/include/haproxy/quic_conn-t.h
+++ b/include/haproxy/quic_conn-t.h
@@ -653,7 +653,6 @@
 
 	struct quic_cid odcid; /* First DCID used by client on its Initial packet. */
 	struct quic_cid dcid; /* DCID of our endpoint - not updated when a new DCID is used */
-	struct ebmb_node scid_node; /* used only for client side (backend) */
 	struct quic_cid scid; /* first SCID of our endpoint - not updated when a new SCID is used */
 	struct eb_root cids; /* tree of quic_connection_id - used to match a received packet DCID with a connection */
 	uint64_t next_cid_seq_num;
diff --git a/src/quic_conn.c b/src/quic_conn.c
index 98b376e..e5d6c25 100644
--- a/src/quic_conn.c
+++ b/src/quic_conn.c
@@ -5670,7 +5670,6 @@
 		tasklet_free(qc->wait_event.tasklet);
 
 	/* remove the connection from receiver cids trees */
-	ebmb_delete(&qc->scid_node);
 	free_quic_conn_cids(qc);
 
 	conn_ctx = qc->xprt_ctx;