Tweak repaint timeout to 5ms after vblank

Reduces risk of flicker, but we need something better here.
diff --git a/wayland-system-compositor.c b/wayland-system-compositor.c
index 4ea7bbd..1d6d0af 100644
--- a/wayland-system-compositor.c
+++ b/wayland-system-compositor.c
@@ -597,7 +597,7 @@
 			      &compositor->base,
 			      compositor->current_frame, msecs);
 
-	wl_event_source_timer_update(compositor->timer_source, 10);
+	wl_event_source_timer_update(compositor->timer_source, 5);
 	compositor->repaint_on_timeout = 1;
 
 	animate = container_of(compositor->animate_list.next, struct wlsc_animate, link);