Revert any changes toward pipewire instead of PulseAudio in Crimson for Librem 5

We're deferring the change to pipewire to Dawn in order to release Crimson.

From Librem5/OS-issues#333 and pureos/core/pureos-meta!3, it seems that there may be some changes toward pipewire already (perhaps from Debian). Revert this to remain on PulseAudio in this release.

Complete when clean flash of Crimson images has working audio with PulseAudio. (Upgrading from byzantium is not required yet, it will be addressed in the next milestone.)