main/postmarketos-ui-console: do not install any audio backend by default

Users who want pulseaudio or pipewire (for audio) can still install them, but by removing any audio backend by default we can avoid creating images that include pulseaudio/gstreamer/mesa.

Before:

$ ls -hal /home/clayton/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-aarch64.img
-rw-r--r-- 1 root 12345 1.1G Feb 10 14:49 /home/clayton/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-aarch64.img

After:

$ ls -hal /home/clayton/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-aarch64.img
-rw-r--r-- 1 root 12345 806M Feb 10 14:49 /home/clayton/.local/var/pmbootstrap/chroot_native/home/pmos/rootfs/qemu-aarch64.img