[GAMEPLAY] Thresh's ultimate applies deathfire touch as an area of effect ability

Thresh's ultimate used to do damage and apply spell effects to all enemies hit by the walls, but now it only applies damage and spell effects to the first enemy to hit a wall. But it wasn't changed to count as a single target ability, despite only applying spell effects to a single target. Another example of an ability which only damages one target but applies CC to multiple targets is Tristana's ultimate, which correctly applies deathfire touch as a single target ability to the original target.