cd557f0636
Lattices would give the choice of going to weightpaint mode (which would
fail immediately because of `vwpaint::mode_toggle_poll_test`) because it
was marked as a compatible mode in `ED_object_mode_compat_test`.
I dont think this was ever supported properly, why this was marked as a
compatible mode is unknown (I stopped tracing git history at
deebf4f8f0).
Even if it was at some point, weightpaint mode nowadays is totally
depended on Mesh, so seems better to just remove it from Lattices.
Pull Request: https://projects.blender.org/blender/blender/pulls/112411