df68dc5768
When panels in node groups were introduced, the interface data of a tree was moved from `tree.inputs_legacy/outputs_legacy` to `tree.tree_interface`. For forward compatibility, the old interface was still written. Since Blender 4.5 can read the new format and older versions are not able to open files created in 5.0 directly anymore, it's fine to remove this forward-compatibility code now. Also fixes #145278. Pull Request: https://projects.blender.org/blender/blender/pulls/145489