[neon-notifications] Dev Required: libxmlb - 0.3.8

[Neon CI]

https://build.neon.kde.org/job/watcher_release_backports-focal_libxmlb/112/display/redirect

#<Debian::UScan::DEHS::Package:0x000055ec2b40c8e8 @name="libxmlb", @debian_uversion="0.3.6", @debian_mangled_uversion="0.3.6", @upstream_version="0.3.8", @upstream_url="https://github.com/hughsie/libxmlb/archive/refs/tags/0.3.8.tar.gz", @status="Newer version available">