[neon-notifications] digikam new version 6.4.0

[Neon CI]

https://build.neon.kde.org/job/watcher_release_neon-packaging_digikam/856/display/redirect

#<Debian::UScan::DEHS::Package:0x0000563a71ad9790 @name="digikam", @debian_uversion="6.3.0", @debian_mangled_uversion="6.3.0", @upstream_version="6.4.0", @upstream_url="http://download.kde.internal.neon.kde.org/stable/digikam/6.4.0/digikam-6.4.0.tar.xz", @status="Newer version available">