No need to send surface.leave/enter events

The scene graph implementation sends these for us, and it does so more
accurately than our overly-simplified approach.  Layer shell surfaces
don't appear to receive these events at all, according to my
WAYLAND_DEBUG experiments with bemenu and dtao.

ΔSLOC: -4

dwl.c

@@ -1525,7 +1525,6 @@ void
 maplayersurfacenotify(struct wl_listener *listener, void *data)
 {
 	LayerSurface *l = wl_container_of(listener, l, map);
-	wlr_surface_send_enter(l->layer_surface->surface, l->mon->wlr_output);
 	motionnotify(0);
 }
 
@@ -2091,15 +2090,12 @@ setmon(Client *c, Monitor *m, uint32_t newtags)
 	c->mon = m;
 	c->prev = c->geom;
 
-	/* TODO leave/enter is not optimal but works */
-	if (oldmon) {
-		wlr_surface_send_leave(client_surface(c), oldmon->wlr_output);
+	/* Scene graph sends surface leave/enter events on move and resize */
+	if (oldmon)
 		arrange(oldmon);
-	}
 	if (m) {
 		/* Make sure window actually overlaps with the monitor */
 		resize(c, c->geom, 0);
-		wlr_surface_send_enter(client_surface(c), m->wlr_output);
 		c->tags = newtags ? newtags : m->tagset[m->seltags]; /* assign tags of target monitor */
 		setfullscreen(c, c->isfullscreen); /* This will call arrange(c->mon) */
 	}