xwm: delete dead flags from weston_wm_window_draw_decorations()

Obviously unused. Looks like weston_wm_window_activate() is doing that
job.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
1 file changed