gdk/toplevel: fix declarations of GdkToplevelSize
GDK_AVAILABLE_IN_ALL was missing from gdk_toplevel_size_get_bounds and gdk_toplevel_size_set_max_size was declared though it doesn't exist.
GDK_AVAILABLE_IN_ALL was missing from gdk_toplevel_size_get_bounds and gdk_toplevel_size_set_max_size was declared though it doesn't exist.