community/openrc-settingsd: remove dbus autolaunch

D-Bus activation does not respect the options configured on /etc/conf.d and could race with the launch of openrc-settingsd from openrc. So let's remove the service files and expect the user to rc-update the openrc-settingsd service instead.

Reference: https://gitlab.com/postmarketOS/pmaports/-/merge_requests/3953