touch.pa: don't set any sink/source as configured default

Since Pulseaudio 11, if any sink or source is configured to be a default, the whole logic which automatically switch a default sink or source to e.g. a bluetooth headset gets overridden. Since we want to have the default sink switched to a Bluetooth headset when it's connected, don't configure any default. The PA's built-in default selection seems to do the right thing already.

Also remove module-default-device-restore, as a.) we don't have any UI to switch a default so it's not so useful and b.) it mitigates issues on devices which already have a default configured and saved.