Cleanup: Remove unused lay_updated

Is no longer used, having it around was more of a confusion than
anything else.

source/blender/blenloader/intern/readfile.c

@@ -6244,7 +6244,6 @@ static void direct_link_scene(FileData *fd, Scene *sce)
 	sce->depsgraph_hash = NULL;
 	sce->fps_info = NULL;
 	sce->customdata_mask_modal = 0;
-	sce->lay_updated = 0;
 
 	BKE_sound_create_scene(sce);
 

source/blender/editors/render/render_internal.c

@@ -734,24 +734,11 @@ static void render_endjob(void *rjv)
 
 	/* Finally unlock the user interface (if it was locked). */
 	if (rj->interface_locked) {
-		Scene *scene;
-
 		/* Interface was locked, so window manager couldn't have been changed
 		 * and using one from Global will unlock exactly the same manager as
 		 * was locked before running the job.
 		 */
 		WM_set_locked_interface(G_MAIN->wm.first, false);
-
-		/* We've freed all the derived caches before rendering, which is
-		 * effectively the same as if we re-loaded the file.
-		 *
-		 * So let's not try being smart here and just reset all updated
-		 * scene layers and use generic DAG_on_visible_update.
-		 */
-		for (scene = G_MAIN->scene.first; scene; scene = scene->id.next) {
-			scene->lay_updated = 0;
-		}
-
 		DEG_on_visible_update(G_MAIN, false);
 	}
 }

source/blender/makesdna/DNA_scene_types.h

@@ -1490,7 +1490,7 @@ typedef struct Scene {
 
 	unsigned int lay;			/* bitflags for layer visibility */
 	int layact;		/* active layer */
-	unsigned int lay_updated;       /* runtime flag, has layer ever been updated since load? */
+	unsigned int pad1;
 
 	short flag;								/* various settings */