nixos/k3s: Use `optional` for more idiomatic code

Changed files
+1 -1
nixos
modules
services
cluster
+1 -1
nixos/modules/services/cluster/k3s/default.nix
···
systemd.services.k3s = {
description = "k3s service";
-
after = [ "network-online.service" "firewall.service" ] ++ (if cfg.docker then [ "docker.service" ] else []);
wants = [ "network-online.service" "firewall.service" ];
wantedBy = [ "multi-user.target" ];
serviceConfig = {
···
systemd.services.k3s = {
description = "k3s service";
+
after = [ "network-online.service" "firewall.service" ] ++ (optional cfg.docker "docker.service");
wants = [ "network-online.service" "firewall.service" ];
wantedBy = [ "multi-user.target" ];
serviceConfig = {