Fix #123882: Ocean Modifier not updating normals in "Displace" mode

Exposed by 383a145a19

The real culprit was in 6a3c3c77b3 though (where the original meshes
normals were tagged dirty instead of the result's).

So to resolve, now tag the result (not the original).

Pull Request: https://projects.blender.org/blender/blender/pulls/123893

source/blender/modifiers/intern/MOD_ocean.cc

@@ -442,7 +442,7 @@ static Mesh *doOcean(ModifierData *md, const ModifierEvalContext *ctx, Mesh *mes
     }
   }
 
-  mesh->tag_positions_changed();
+  result->tag_positions_changed();
 
   if (allocated_ocean) {
     BKE_ocean_free(omd->ocean);