[neon-notifications] Dev Required: qt6-mqtt - 6.9.0-beta2

[Neon CI]

https://build.neon.kde.org/job/watcher_release_qt6_qt6-mqtt/174/display/redirect

#<Debian::UScan::DEHS::Package:0x000078a05d75fd20 @name="qt6-mqtt", @debian_uversion="6.8.1", @debian_mangled_uversion="6.8.1", @upstream_version="6.9.0-beta2", @upstream_url="https://github.com/qt/qtmqtt/archive/refs/tags/v6.9.0-beta2.tar.gz", @status="Newer version available">