speakersafetyd: d/rules: override dh_installsystemd
I talked to the Asahi team, and was told that speakersafetyd.service should never be enabled in systemd, but rather only triggered by the udev rules. (I myself had issues caused by the service failing when running in a VM). This MR implements this requirement. Installation of the systemd service is done within the execute_after_dh_install target, so overriding dh_installsystemd only disables auto-activation and auto-start of the service.