Make clean or sdw-admin --uninstall does not remove sd-rsyslog.conf in whonix-gw-15

[emkll]

When uninstalling or running make clean in a dev environment, at least one file is not removed from the default Qubes-provided whonix-gw-15 template: /etc/sd-rsyslog.conf. We should probably do so in https://github.com/freedomofpress/securedrop-workstation/blob/main/dom0/sd-clean-whonix.sls#L14