Fix #115572: shape_key_remove operator leaves shared normals

Caused by 383a145a19

Since above commit, normals were in a SharedCache, they need to be tagged dirty
for recalculation.

Instead of tagging the normals caches dirty explicitly, simply use
`BKE_mesh_tag_positions_changed` [which includes all this and also tags
positions dirty - which sounds also needed for updating other things]

Pull Request: https://projects.blender.org/blender/blender/pulls/115580

source/blender/blenkernel/intern/key.cc

@@ -1605,6 +1605,7 @@ float *BKE_key_evaluate_object_ex(
         const int totvert = min_ii(tot, mesh->totvert);
         mesh->vert_positions_for_write().take_front(totvert).copy_from(
             {reinterpret_cast<const blender::float3 *>(out), totvert});
+        BKE_mesh_tag_positions_changed(mesh);
         break;
       }
       case ID_LT: {