package/qt6: bump version to 6.4.2
For details see [1] and [2].
[1] https://code.qt.io/cgit/qt/qtreleasenotes.git/about/qt/6.4.1/release-note.md
[2] https://code.qt.io/cgit/qt/qtreleasenotes.git/about/qt/6.4.2/release-note.md
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Tested-by: Angelo Compagnucci <angelo@amarulasolutions.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>