fix #40641: incorrect import/export of relative-x

As discussed in issue, I think it makes sense for now to simply not import or export relative-x for chord symbols, since we don't do it for any other elements.  There is an existing "todo" note regarding support of offsets and relative-x.  I left the relative-x in but commented it out to have for reference if/wehn the time comes to revisit any of this.  It seems that is also the approach taken for various other places where relative-x was being used or considered for use at one time.