[neon-notifications] Dev Required: flatpak - 1.13.1

[Neon CI]

https://build.neon.kde.org/job/watcher_release_backports-focal_flatpak/174/display/redirect

#<Debian::UScan::DEHS::Package:0x000055f7ba8e2d00 @name="flatpak", @debian_uversion="1.12.4", @debian_mangled_uversion="1.12.4", @upstream_version="1.13.1", @upstream_url="https://github.com/flatpak/flatpak/releases/download/1.13.1/flatpak-1.13.1.tar.xz", @status="Newer version available">