nixos/tarsnap: update doc for printStats

after the change made in 15567e6d8e338f339e4fafada1362bdaa9612cb3

Changed files
+1 -1
nixos
modules
services
backup
+1 -1
nixos/modules/services/backup/tarsnap.nix
···
description = ''
Print global archive statistics upon completion.
The output is available via
-
<command>systemctl status tarsnap@archive-name</command>.
+
<command>systemctl status tarsnap-archive-name</command>.
'';
};