Nandi and Mangrove dataset links broken

[legel]

From nandi.md , the link to the rslearn dataset is broken:

https://huggingface.co/datasets/allenai/olmoearth_projects_nandi/blob/main/dataset.tar

[legel]

Also mangrove.md has broken links, at least:

https://huggingface.co/allenai/olmoearth_projects_mangrove/resolve/main/mangrove.tar
https://huggingface.co/allenai/olmoearth_projects_mangrove/blob/main/annotation_features.geojson