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