CLEANUP: mux-quic: remove uneeded TODO in qc_detach

The stream mux buffering has been reworked since the introduction of the
struct qc_stream_desc. A qcs is now able to quickly release its buffer
to the quic-conn.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 8b85c33..b913189 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1061,11 +1061,6 @@
 
 	TRACE_ENTER(QMUX_EV_STRM_END, qcc->conn, qcs);
 
-	/* TODO on CONNECTION_CLOSE reception, it should be possible to free
-	 * qcs instances. This should be done once the buffering and ACK
-	 * managment between xprt and mux is reorganized.
-	 */
-
 	--qcc->nb_cs;
 
 	if ((b_data(&qcs->tx.buf) || qcs->tx.offset > qcs->tx.sent_offset) &&