One of the oldest items in the game, Sheen's ability power always made it a little awkward to use as a building block for other items (like Iceborn Gauntlet, which was always pretty confusing). Removing AP and adding cooldown reduction adds more synergies for the champions who want the Spellblade passive without forcing an often-'wasted' stat on them.
TOTAL cost : [1250 gold] ⇒ 1050 gold
BUILD path : Sapphire Crystal + 700 gold
mana :  ⇒ 250
ABILITY power  ⇒ 0
COOLDOWN reduction [0%] ⇒ 10%