CLEANUP: mux-quic: change comment style to not mess with git conflict

Remove "=======" symbols from the MUX buffer diagram. This is useful to
not mess with git conflict markers when resolving a conflict.
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 87be58c..9dc4c40 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -367,9 +367,9 @@
 	 * QCS out buffer diagram
 	 *             head           left    to_xfer
 	 *         -------------> ----------> ----->
-	 * ==================================================
+	 * --------------------------------------------------
 	 *       |...............|xxxxxxxxxxx|<<<<<
-	 * ==================================================
+	 * --------------------------------------------------
 	 *       ^ ack-off       ^ sent-off  ^ off
 	 *
 	 * STREAM frame