Using a list of multi-dim numpy arrays raises an error "can only convert 1-dimensional array values"
This error has been introduced in https://github.com/huggingface/datasets/pull/2361

To reproduce:
```python
import numpy as np
from datasets import Dataset

d = Dataset.from_dict({"a": [np.zeros((2, 2))]})
```
raises
```python
Traceback (most recent call last):
  File "playground/ttest.py", line 5, in <module>
    d = Dataset.from_dict({"a": [np.zeros((2, 2))]}).with_format("torch")
  File "/Users/quentinlhoest/Desktop/hf/nlp/src/datasets/arrow_dataset.py", line 458, in from_dict
    pa_table = InMemoryTable.from_pydict(mapping=mapping)
  File "/Users/quentinlhoest/Desktop/hf/nlp/src/datasets/table.py", line 365, in from_pydict
    return cls(pa.Table.from_pydict(*args, **kwargs))
  File "pyarrow/table.pxi", line 1639, in pyarrow.lib.Table.from_pydict
  File "pyarrow/array.pxi", line 332, in pyarrow.lib.asarray
  File "pyarrow/array.pxi", line 223, in pyarrow.lib.array
  File "pyarrow/array.pxi", line 110, in pyarrow.lib._handle_arrow_array_protocol
  File "/Users/quentinlhoest/Desktop/hf/nlp/src/datasets/arrow_writer.py", line 107, in __arrow_array__
    out = pa.array(self.data, type=type)
  File "pyarrow/array.pxi", line 306, in pyarrow.lib.array
  File "pyarrow/array.pxi", line 39, in pyarrow.lib._sequence_to_array
  File "pyarrow/error.pxi", line 143, in pyarrow.lib.pyarrow_internal_check_status
  File "pyarrow/error.pxi", line 99, in pyarrow.lib.check_status
pyarrow.lib.ArrowInvalid: Can only convert 1-dimensional array values