For now, Yasuo's Wall should not block Zilean's bomb

Leave it as a projectile but give it a special passive where it ignores any projectile-blocking abilities.

Just for now, seeing as that is currently Zilean's only ability that can be used for combat. It's fine for champs who happen to have a projectile or who focus an auto attacks, but Zilean's bomb is the only thing he's got, and two of them aren't even enough to kill a person.