Tweak systemd unit file
Tweak systemd unit file

The directive "StartLimitInterval" has been replaced by [StartLimitIntervalSec=interval, StartLimitBurst=burst](https://www.freedesktop.org/software/systemd/man/systemd.unit.html#StartLimitIntervalSec=interval). I'd suggest that the default backoff settings are fine (in Ubuntu 19.10 no more than 5 restarts per 10 seconds, else delayed by 10 seconds per attempt) so this directive can simply be removed.
restic/rest-server,restic/rest-server