Codefix: Add missing const inside script functions. (#12794)

Scripts do not modify items directly, marking them const enforces this.

src/script/api/script_stationlist.cpp

@@ -32,7 +32,7 @@ ScriptStationList_Vehicle::ScriptStationList_Vehicle(VehicleID vehicle_id)
 {
 	if (!ScriptVehicle::IsPrimaryVehicle(vehicle_id)) return;
 
-	Vehicle *v = ::Vehicle::Get(vehicle_id);
+	const Vehicle *v = ::Vehicle::Get(vehicle_id);
 
 	for (Order *o = v->GetFirstOrder(); o != nullptr; o = o->next) {
 		if (o->IsType(OT_GOTO_STATION)) this->AddItem(o->GetDestination());