Link to TUM FACADE dataset is invalid

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D-ML/issues).
- [X] I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `main` branch).

### Describe the issue

The link mentioned in https://github.com/isl-org/Open3D-ML/blob/main/ml3d/datasets/tumfacade.py for the processed data is invalid.

https://tumde-my.sharepoint.com/:f:/g/personal/olaf_wysocki_tum_de/EjA8B_KGDyFEulRzmq-CG1QBBL4dZ7z5PoHeI8zMD0JxIQ?e=9MrMcl.

With the link gone the TUM FACADE dataset can't really be used at all.

@ThomasFroech, can you update this please?