Provide the winning team's name in the match with the point of winning margin of 7 on May 7, 2009.
the winning team refers to Team_Id = Match_Winner; the point of winning margin of 7 refers to Win_Margin = 7; on May 7 2009 refers to Match_Date = '2009-05-07'
SELECT T1.Team_Name FROM Team AS T1 INNER JOIN Match AS T2 ON T1.Team_Id = T2.Match_Winner WHERE T2.Match_Date = '2009-05-07' AND T2.Win_Margin = 7