made the shapes within the ExpandCollapseButton non-pickable in order to reduce hit testing, recommened by @jonathanolson while working on  https://github.com/phetsims/build-an-atom/issues/38
made the shapes within the ExpandCollapseButton non-pickable in order to reduce hit testing, recommened by @jonathanolson while working on  https://github.com/phetsims/build-an-atom/issues/38

phetsims/sun,phetsims/sun,phetsims/sun