fix restore window size by using ResizeBy -> ResizeTo

This PR fixes restored window size is bigger than expecting (ref: https://github.com/FancyWM/fancywm/issues/346). `savedLocation.Parent.Attach` has already secured space, so `SizeTo` is appropriate in this situation. I comfirm this change works rightly with building on my environment. Thank @veselink1 for developping this great project for people on Windows hoping tiling window manager !