By Scott Trotter Former Arsenal defender Martin Keown has ripped into Manchester United’s efforts after squandering their lead against Chelsea in a 4-3 defeat. The outspoken pundit did not even spare two-goal Alejandro Garnacho as he criticised the winger’s celebrations after putting the Red Devils ahead. Garnacho sat on an advertising board at Stamford Bridge after handing United an advantage to make the score 3-2 with 67 minutes gone. Erik ten Hag’s side led until the 100th minute when Cole Palmer converted from the penalty spot to level the scores. The former Man City ace then caught United…