X11 fractional scaling creates nonsensical windowSizeIncrements

Making the resize increment increase with scale makes sense for integer scaling, as our requested window manager sizes will match sizes we can represent in our logical co-ordinate space.
This is not true for fractional scaling.

If a fractional scale of 2.5 is used our NETWM resize increment is set to 3. Which will create gaps where window manager tries to lay things out. It doesn't add anything as it still is a size that can't be mapped to a logical size cleanly.

With fractional scaling we're always going to have a discrepancy, but if we can't make things match exactly it's going to give more accurate results if the resizeIncrement is left alone at 1,1.

Relevant code is  QPlatformWindow::windowSizeIncrement()

Downstream issue: https://bugs.kde.org/show_bug.cgi?id=391956