Fix missing comma between parameters

Author: souravsingh

axelrod/strategies/titfortat.py

@@ -637,7 +637,7 @@ def strategy(self, opponent: Player) -> Action:
         # Otherwise play previous move
         return self.history[-1]
 
-@FinalTransformer((D,) name_prefix=None)
+@FinalTransformer((D,), name_prefix=None)
 class Alexei(Player):
     """
     Plays similar to Tit-for-Tat, but always defect on last turn.