chore(valheim): select butter-chicken world

configs/nixos/hosts/pikachu/default.nix

@@ -73,7 +73,7 @@
     steamPath = "/pikachu/data/steamcmd";
     installPath = "/pikachu/data/servers/valheim/main";
     statePath = "/pikachu/media/games/servers/valheim/main";
-    serverName = "main";
+    serverName = "butter-chicken";
     reverseProxy = {
       enable = true;
       route = {