gdkwindow-win32: Remove queue_antiexpose implementation

gdkwindow-win32: Remove queue_antiexpose implementation

Since the Win32 code never actually called InvalidateRgn or used the
Win32 update area at all, that meant the only thing that could possibly
invalidate the window was the Win32 window manager as part of scrolling
or resizing, which would also send it a WM_PAINT message.

But the WM_PAINT handling called BeginPaint / EndPaint, which clears the
update area completely! We also draw out-of-band, not directly when
handling WM_PAINT, so there's no way that the update area inside the
Win32 WM would match our local one.

There is no possible way that this queue_antiexpose implementation could
do anything. Remove it.