Fallback on dataset script if user wants to load default config
Right now this code is failing on `main`:

```python
load_dataset("openbookqa")
```

This is because it tries to load the dataset from the Parquet export but the dataset has multiple configurations and the Parquet export doesn't know which one is the default one.

I fixed this by simply falling back on using the dataset script (which tells the user to pass `trust_remote_code=True`):

```python
load_dataset("openbookqa", trust_remote_code=True)
```

Note that if the user happened to specify a config name I don't fall back on the script since we can use the Parquet export in this case (no need to know which config is the default)


```python
load_dataset("openbookqa", "main")
```