Set RestartSec=1m in litewitness systemd service file

Set RestartSec=1m in roles/litewitness/templates/litewitness@.service.j2 file.

The idea is that when the service fails, we want to keep trying to restart it but not too often. This should help avoid giving up due to start rate limiting, and also avoid spamming too frequent error messages.

More reasoning behind this: If the failure happens because a transparency log that the witness tries to communicate with is down och behaving badly, then it is probably good to keep trying with some delay between attempts, so that the witness starts working again if/when the transparency log becomes available again.