[neon-notifications] Dev Required: flatpak - 1.12.6

[Neon CI]

https://build.neon.kde.org/job/watcher_release_backports-focal_flatpak/155/display/redirect

#<Debian::UScan::DEHS::Package:0x0000563289c19a78 @name="flatpak", @debian_uversion="1.12.4", @debian_mangled_uversion="1.12.4", @upstream_version="1.12.6", @upstream_url="https://github.com/flatpak/flatpak/releases/download/1.12.6/flatpak-1.12.6.tar.xz", @status="Newer version available">