Change QDialogButtonBox::KdeLayout Order to Match Downstream Proposal

The QDialogButtonBox::KdeLayout is hardcoded to Ok | Apply | Cancel.  Recently, there has been a discussion downstream about changing this to Apply | Cancel | Ok.  The consensus was that there is no good way to do this without changing the hardcoded value upstream or allowing it to be configured through a text file.

As such, I propose changing the layout to match the proposed Apply | Cancel | Ok.

Discussion is here:

https://bugs.kde.org/show_bug.cgi?id=472733