The version of the pulseaudio package in Buster has no epoch, so
`Breaks: pulseaudio (<< 1:8.0-0ubuntu3co4~)` causes APT to uninstall pulseaudio
or chaiwala-apparmor-profiles when the other is installed.

With the curren recipes this causes chaiwala-apparmor-profiles to be removed as
pulseaudio is installed later.

Drop the reference to old Ubuntu versions both for pulseaudio and apparmor now
that we moved on top of Debian Buster.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>