ArrayXD with None as leading dim incompatible with DatasetCardData
It looks like `CardData` in `huggingface_hub` removes None values where it shouldn't. Indeed it calls `_remove_none` on the return of `to_dict()`:

```python
    def to_dict(self) -> Dict[str, Any]:
        """Converts CardData to a dict.

        Returns:
            `dict`: CardData represented as a dictionary ready to be dumped to a YAML
            block for inclusion in a README.md file.
        """

        data_dict = copy.deepcopy(self.__dict__)
        self._to_dict(data_dict)
        return _remove_none(data_dict)
```

Would it be ok to remove `list()` from being scanned in `_remove_none` ? it could also be a specific behavior to DatasetCardData if necessary @Wauplin  I have actually no idea why none values are removed in model and dataset card data... :see_no_evil:
Looks like `_remove_none` has been introduced at the same time as the entire repocard module (see https://github.com/huggingface/huggingface_hub/pull/940). I would be tempted to remove `_remove_none` entirely actually and only remove "top-level" None values (i.e. if something like `pipeline_tag=None` due to a default value in kwargs => we remove it). Hard to tell what could be the side effects but I'm not against trying.


However, I'm not really in favor in making an exception only for lists. It would mean that tuples, sets and dicts are filtered but not lists, which is pretty inconsistent. let's do it for top level attributes yes I opened https://github.com/huggingface/huggingface_hub/pull/2626 to address it :) thanks !
### Describe the bug

Creating a dataset with ArrayXD features leads to errors when downloading from hub due to DatasetCardData removing the Nones

@lhoestq 

### Steps to reproduce the bug

```python
import numpy as np
from datasets import Array2D, Dataset, Features, load_dataset

def examples_generator():
    for i in range(4):
        yield {
            "array_1d": np.zeros((10,1), dtype="uint16"),
            "array_2d": np.zeros((10, 1), dtype="uint16"),
        }

features = Features(array_1d=Array2D((None,1), "uint16"), array_2d=Array2D((None, 1), "uint16"))
dataset = Dataset.from_generator(examples_generator, features=features)
dataset.push_to_hub("alex-hh/test_array_1d2d")
ds = load_dataset("alex-hh/test_array_1d2d")
```

Source of error appears to be DatasetCardData.to_dict invoking DatasetCardData._remove_none
```python
from huggingface_hub import DatasetCardData
from datasets.info import DatasetInfosDict

dataset_card_data = DatasetCardData()
DatasetInfosDict({"default": dataset.info.copy()}).to_dataset_card_data(dataset_card_data)
print(dataset_card_data.to_dict())  # removes Nones in shape
```

### Expected behavior

Should be possible to load datasets saved with shape None in leading dimension

### Environment info

3.0.2 and latest huggingface_hub