Doc: Update Copyright in md4c license text

Amends c29a235

[ChangeLog][Third-Party Code] Updated md4c (optional part of
Qt Gui) to version 0.5.1.

Change-Id: I7c41fc65fbc92670c1fe4bd0b6d2f46674bdb435
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
(cherry picked from commit c92de95)
(cherry picked from commit 73cf291)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 64736d2)

src/3rdparty/md4c/LICENSE.md

@@ -1,7 +1,7 @@
 
 # The MIT License (MIT)
 
-Copyright © 2016-2020 Martin Mitáš
+Copyright © 2016-2024 Martin Mitáš
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the “Software”),