In the matches where the winning margin is less than fifty, how many teams won by wicket?
winning margin is less than fifty refers to Win_Margin < 50; won by wicket refers to Win_Type = 'wickets'
SELECT COUNT(T2.Win_Id) FROM `Match` AS T1 INNER JOIN Win_By AS T2 ON T1.Win_Type = T2.Win_Id WHERE T2.Win_Type = 'wickets' AND T1.Win_Margin < 50