Remove `extended` field from dataset tagger
The tagger also doesn't insert the value for the `size_categories` field automatically, so this should be fixed too Thanks for reporting. Indeed the `extended` tag doesn't exist. Not sure why we had that in the tagger.
The repo of the tagger is here if someone wants to give this a try: https://github.com/huggingface/datasets-tagging
Otherwise I can probably fix it next week I've opened a PR on `datasets-tagging` to fix the issue 🚀  thanks ! this is fixed now
## Describe the bug
While working on #2435 I used the [dataset tagger](https://huggingface.co/datasets/tagging/) to generate the missing tags for the YAML metadata of each README.md file. However, it seems that our CI raises an error when the `extended` field is included:

```
dataset_name = 'arcd'

    @pytest.mark.parametrize("dataset_name", get_changed_datasets(repo_path))
    def test_changed_dataset_card(dataset_name):
        card_path = repo_path / "datasets" / dataset_name / "README.md"
        assert card_path.exists()
        error_messages = []
        try:
            ReadMe.from_readme(card_path)
        except Exception as readme_error:
            error_messages.append(f"The following issues have been found in the dataset cards:\nREADME:\n{readme_error}")
        try:
            DatasetMetadata.from_readme(card_path)
        except Exception as metadata_error:
            error_messages.append(
                f"The following issues have been found in the dataset cards:\nYAML tags:\n{metadata_error}"
            )
    
        if error_messages:
>           raise ValueError("\n".join(error_messages))
E           ValueError: The following issues have been found in the dataset cards:
E           YAML tags:
E           __init__() got an unexpected keyword argument 'extended'

tests/test_dataset_cards.py:70: ValueError
```

Consider either removing this tag from the tagger or including it as part of the validation step in the CI.

cc @yjernite 