nixos/opensnitch: fix typo and enable new system rules

Fixed typo to enable [new system rules](https://github.com/evilsocket/opensnitch/wiki/System-rules#upgrading-from-previous-versions)

Fixes: https://github.com/NixOS/nixpkgs/issues/256290

Changed files
+1 -1
nixos
modules
services
security
+1 -1
nixos/modules/services/security/opensnitch.nix
···
ln -sf '${file}' "${local}"
'') rules}
-
if [ ! -f /etc/opensnitch-system-fw.json ]; then
+
if [ ! -f /etc/opensnitchd/system-fw.json ]; then
cp "${pkgs.opensnitch}/etc/opensnitchd/system-fw.json" "/etc/opensnitchd/system-fw.json"
fi
'');