group example json is down

I checked the documentation on group here: https://epgg.github.io/datahub/track_properties#group

This mentions an example json, https://wangftp.wustl.edu/~dli/test/a-group.json, but this seems to be down.

I get the following error:

<img width="843" height="323" alt="Image" src="https://github.com/user-attachments/assets/989379af-1f2b-4355-a352-1f91f9aa74c5" />