Fix #9209: Excessive time resizing highscore/news window when screen is too small. (#9210)

If the highscore/news window panel size, which is now scaled by GUI zoom, is larger than the screen size, a loop will be entered where the window is repeatedly resized.

This is resolved by removing the minimal size from the panel, as the window is always resized to cover the screen anyway. This means the screen size can never be too small.