datasets.config.PYARROW_VERSION has no attribute 'major'
In the test_dataset_common.py script, line 288-289

```
if datasets.config.PYARROW_VERSION.major < 3:
   packaged_datasets = [pd for pd in packaged_datasets if pd["dataset_name"] != "parquet"]
```

which throws the error below. `datasets.config.PYARROW_VERSION` itself return the string '4.0.1'. I have tested this on both datasets.__version_=='1.11.0' and '1.9.0'. I am using Mac OS.

```
import datasets
datasets.config.PYARROW_VERSION.major
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/var/folders/1f/0wqmlgp90qjd5mpj53fnjq440000gn/T/ipykernel_73361/2547517336.py in <module>
      1 import datasets
----> 2 datasets.config.PYARROW_VERSION.major

AttributeError: 'str' object has no attribute 'major'
```

## Environment info
- `datasets` version: 1.11.0
- Platform: Darwin-20.6.0-x86_64-i386-64bit
- Python version: 3.7.11
- PyArrow version: 4.0.1
