Fix: Missing multires to faces visibility sync after box hide

The operator handled faces visibility change correctly but not
multires. Use the existing PBVH API function for that, also remove
a redundant call to the function that fetched the attribute pointers
again after the change.

source/blender/editors/sculpt_paint/paint_hide.cc

@@ -382,9 +382,8 @@ static int hide_show_exec(bContext *C, wmOperator *op)
 
   /* Ensure that edges and faces get hidden as well (not used by
    * sculpt but it looks wrong when entering editmode otherwise). */
-  if (pbvh_type == PBVH_FACES) {
-    BKE_mesh_flush_hidden_from_verts(me);
-    BKE_pbvh_update_hide_attributes_from_mesh(pbvh);
+  if (ELEM(pbvh_type, PBVH_FACES, PBVH_GRIDS)) {
+    BKE_pbvh_sync_visibility_from_verts(pbvh, me);
   }
 
   RegionView3D *rv3d = CTX_wm_region_view3d(C);

source/blender/editors/sculpt_paint/sculpt_undo.cc

@@ -1065,8 +1065,6 @@ static void sculpt_undo_restore_list(bContext *C, Depsgraph *depsgraph, ListBase
       if (ELEM(BKE_pbvh_type(ss->pbvh), PBVH_FACES, PBVH_GRIDS)) {
         Mesh *me = (Mesh *)ob->data;
         BKE_pbvh_sync_visibility_from_verts(ss->pbvh, me);
-
-        BKE_pbvh_update_hide_attributes_from_mesh(ss->pbvh);
       }
 
       BKE_pbvh_update_visibility(ss->pbvh);