Fix arguments of type mismatch error message in wxGTK wxDVC.

The "required" and "actual" arguments were exchanged, making the message
pretty confusing.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78291 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775