accesskit_winit Unix backend seems to be misinterpreting resize event

[mwcampbell]

I was looking at accesskit_winit's event handling, particularly in the Unix backend, to see if there's any way we could avoid requiring the windo parameter. I noticed that our handler for the Resized event treats the size as the outer size. But according to the documentation for the Resized event, that event provides the new size of the client area, which is the inner size. @DataTriny Can you please double check this?