By Toby Cudworth Wayne Rooney offered a reminder that class is permanent after scoring a superb free-kick during a charity game between Manchester United and Celtic on Saturday. United’s all-time record goalscorer has turned his hand to management in recent years, taking charge of Derby County, DC United, Birmingham City and Plymouth Argyle, who appointed him in May on a three-year contract. But the 38-year-old was back in game mode at Old Trafford as he lined up for United in a foundation charity match against Celtic – the first time Rooney had pulled on the club’s famous number 10 jersey sin…