Resolve deprecation warning on importlib

```
DeprecationWarning: open_text is deprecated. Use files() instead. Refer to https://importlib-resources.readthedocs.io/en/latest/using.html#migrating-from-legacy for migration advice.
  with importlib.resources.open_text(data, f"{'gb' if british else 'us'}_gold.json") as r:
```