CLEANUP: mux-quic: adjust comment for coding-style

Replace single-line comment style by /* ... */ format which is the
standard for haproxy documentation.
diff --git a/include/haproxy/mux_quic-t.h b/include/haproxy/mux_quic-t.h
index b2730b7..e7ae233 100644
--- a/include/haproxy/mux_quic-t.h
+++ b/include/haproxy/mux_quic-t.h
@@ -74,10 +74,10 @@
 };
 
 #define QC_SF_NONE              0x00000000
-#define QC_SF_FIN_RECV          0x00000001  // last frame received for this stream
-#define QC_SF_FIN_STREAM        0x00000002  // FIN bit must be set for last frame of the stream
-#define QC_SF_BLK_MROOM         0x00000004  // app layer is blocked waiting for room in the qcs.tx.buf
-#define QC_SF_DETACH            0x00000008  // cs is detached but there is remaining data to send
+#define QC_SF_FIN_RECV          0x00000001  /* last frame received for this stream */
+#define QC_SF_FIN_STREAM        0x00000002  /* FIN bit must be set for last frame of the stream */
+#define QC_SF_BLK_MROOM         0x00000004  /* app layer is blocked waiting for room in the qcs.tx.buf */
+#define QC_SF_DETACH            0x00000008  /* cs is detached but there is remaining data to send */
 
 struct qcs {
 	struct qcc *qcc;