desktop-shell: Stop asking for a RGB565 background

This makes the background image look much nicer, at the expense of
slightly more memory bandwidth used.

Signed-off-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Daniel Stone <daniels@collabora.com>

clients/desktop-shell.c

@@ -1101,8 +1101,6 @@ background_create(struct desktop *desktop)
 	window_set_user_data(background->window, background);
 	widget_set_redraw_handler(background->widget, background_draw);
 	widget_set_transparent(background->widget, 0);
-	window_set_preferred_format(background->window,
-				    WINDOW_PREFERRED_FORMAT_RGB565);
 
 	s = weston_config_get_section(desktop->config, "shell", NULL, NULL);
 	weston_config_section_get_string(s, "background-image",