fix: useUnitMultiplier as optional (#2303)

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packages/core/src/components/cart/CartItem/CartItem.tsx

@@ -62,7 +62,7 @@ function useCartItemEvent() {
 
 interface Props {
   item: ICartItem
-  useUnitMultiplier: boolean
+  useUnitMultiplier?: boolean
 }
 
 function CartItem({ item, useUnitMultiplier = false }: Props) {