Fix example with dynamic drop down list.

The problem is that there is not enough room for the dynamic drop down
list to be inserted above the static drop down list in the drop down
example, so increase the size of the spacer panel between them from 8px
to 70px to make room. Otherwise they overlap, which looks bad. This may
be a bug in Nifty, as it seems like it should make space on the fly
instead of having to manually do it.