Updated ACSS heading font family

Property	Value
description	Updated the ACSS default heading font family from `Head` to `MAC Head`.
stack	Bricks
variant	base
version	1.0.0
type	Update
related	Automatic.css, Updated ACSS config, Custom Fonts

• Updated the default ACSS heading font family from Head to MAC Head.
• Aligned the typography settings with the starter font-family names already used for the shared ACSS custom-font slots.
• Kept the heading stack consistent with the Bricks and Etch boiler naming model.