Remove "normal damage" weakness from cannons

With everyone using bladestorm over firestorm now, one easy way to balance things out is to remove “normal damage weakness” from cannons. This way, firestorm will still have an advantage over bladestorm for a defense filled with cannons. Right now, there is absolutely no reason at all to pick firestorm over bladestorm. Firebolt is NOT a reason because most bases position firebolt outside of bladestorm or firestorm’s range anyway, and firebolt gets destroyed when you reach it either by units or close ranged spells like hammerstrike or sonic

firestorm already has an advantage ovr bladestorm