[neon-notifications] Dev Required: qxmpp - 1.5.6

[Neon CI]

https://build.neon.kde.org/job/watcher_release_backports-jammy_qxmpp-jammy/353/display/redirect

#<Debian::UScan::DEHS::Package:0x00005631a2ebd140 @name="qxmpp", @debian_uversion="1.5.5", @debian_mangled_uversion="1.5.5", @upstream_version="1.5.6", @upstream_url="https://github.com/qxmpp-project/qxmpp/archive/refs/tags/v1.5.6.tar.gz", @status="Newer version available">