[neon-notifications] Dev Required: qt6-mqtt - 6.8.0-rc1

[Neon CI]

https://build.neon.kde.org/job/watcher_release_qt6_qt6-mqtt/111/display/redirect

#<Debian::UScan::DEHS::Package:0x00007b1d0e4bb378 @name="qt6-mqtt", @debian_uversion="6.8.0", @debian_mangled_uversion="6.8.0", @upstream_version="6.8.0-rc1", @upstream_url="https://github.com/qt/qtmqtt/archive/refs/tags/v6.8.0-rc1.tar.gz", @status="Newer version available">