main/postmarketos-base-ui: stop inhibiting sleep/suspend during audio playback

This test is apparently wrong a lot now, so let's disable it. Audio apps should inhibit sleep/suspend on their own, or worst case you can do something like systemd-inhibit <audio app>.

We still want sleep-inhibitor around for now to inhibit sleep/shutdown when an SSH client is connected or when apk is running.

Fixes #3745 (closed)