Merge display of "nonbinary" and "non-binary" in gender display charts

"nonbinary" and "non-binary" are essentially just slightly different ways to write the same thing, so it stands to reason to me that they should be grouped together i.e. in your library's charts + graphs section.

Duplicate of https://www.librarything.com/topic/364735

Sorry, don't know how a duplicate got posted.