fix(issue1206): Need to use unsetZIndex=true in react-draggable-list

[p4p4j0hn]

Fixes #1206 From the docs: unsetZIndex is an optional property that defaults to false. If set to true, then the z-index of all of the list items will be set to "auto" when the list isn't animating. This may have a small performance cost when the list starts and stops animating. Use this if you need to avoid having the list item create a stacking context when it's not being animated.

[mitchdowney]

Just tested and your change worked for me. Thanks for your help!