[ Reason ]
Fixes dialpad tones in Lomiri Phone app

[ Impact ]
lomiri-dialer-app is not installed by default and Lomiri doesn't show
in the Debian Installer list like other desktops in Debian 13.
However, Lomiri does show in the desktop list in Forky. There are some
Debian 13 Lomiri users and we want apps to work as expected there.

[ Tests ]
I built this package on trixie and installed it on Debian 13. I
successfully completed my test case from
https://bugs.debian.org/1139235

[ Risks ]
This only touches the systemd user service which is the part of
tone-generator that was broken and removing an alternate dependency
that isn't supported. This fix has been in Debian Testing since early
June 2026. This set of changes is also proposed as a stable update for
Ubuntu 26.04 LTS.

[ Checklist ]
  [✔️] all changes are documented in the d/changelog
  [✔️] I reviewed all changes and I approve them
  [✔️] attach debdiff against the package in stable
  [✔️] the issue is verified as fixed in unstable

Thank you,
Jeremy Bícha