remove webroot for turn.hacc.space

turn.hacc.space is only there to server acme challanges, it doesn't
need to actually serve files — just the default nginx page is fine.

hosts/hainich/services/workadventure.nix

@@ -87,7 +87,6 @@ in
     # this isn't actually needed, but acme requires a webserver to serve
     # challanges, so I guess it's easier to just define a virtualHost here
     virtualHosts."turn.hacc.space" = {
-      root = "/var/turn-www"; # do we need this, or can acme do with a 404?
       enableACME = true;
       forceSSL = true;
     };