KeyError 'tilejson' on vector tiles probe

**Describe the bug**
we host a vector tile service at https://tiles.isric.org based on [TRex](https://t-rex.tileserver.ch/), when i run the [tilejson](https://tiles.isric.org/wosis.json) through geohealthcheck, i get this error:

```
"class": "GeoHealthCheck.plugins.probe.mapbox.TileJSON",
"message": "Perform_request Err: KeyError 'tilejson'",
"name": "TileJSON",
"probe_id": 1,
"response_time": "0.78631",
"success": false
```

I wonder if this is a problem on our configuration or on the probe, some guidance would be helpfull.