phetsims/sun#137 AccordionBox: eliminate expandedBoxHeight property, it's unnecessary because bounds include invisible children, use  AccordionBox.height in build-an-atom call sites.
phetsims/sun#137 AccordionBox: eliminate expandedBoxHeight property, it's unnecessary because bounds include invisible children, use  AccordionBox.height in build-an-atom call sites.

phetsims/sun,phetsims/sun,phetsims/sun