Fix the comparison function in the list control sample to do what it says.

Fix the comparison function in the list control sample to do what it says.

The comment in the function implied that it exchanged the items but in fact it
did not and kept their existing order instead.

Do revert them now, at least like this something visibly happens in the sample
when the items are sorted.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67734 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775