datasets.load_dataset raises FileNotFoundError for datasets==2.16.0
Hi ! Thanks for reporting

This is a bug in 2.16.0 for some datasets when `cache_dir` is a relative path. I opened https://github.com/huggingface/datasets/pull/6543 to fix this We just released 2.16.1 with a fix:

```
pip install -U datasets
```
### Describe the bug

Seems `datasets.load_dataset` raises FileNotFoundError for some hub datasets with the latest `datasets==2.16.0`

### Steps to reproduce the bug

For example `pip install datasets==2.16.0`
then

```python
import datasets

datasets.load_dataset("wentingzhao/anthropic-hh-first-prompt", cache_dir='cache1')["train"]

```

This will raise:

```bash
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/load.py", line 2545, in load_dataset
    builder_instance.download_and_prepare(
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/builder.py", line 1003, in download_and_prepare
    self._download_and_prepare(
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/builder.py", line 1076, in _download_and_prepare
    split_generators = self._split_generators(dl_manager, **split_generators_kwargs)
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/packaged_modules/parquet/parquet.py", line 43, in _split_generators
    data_files = dl_manager.download_and_extract(self.config.data_files)
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/download/download_manager.py", line 566, in download_and_extract
    return self.extract(self.download(url_or_urls))
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/download/download_manager.py", line 539, in extract
    extracted_paths = map_nested(
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/py_utils.py", line 466, in map_nested
    mapped = [
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/py_utils.py", line 467, in <listcomp>
    _single_map_nested((function, obj, types, None, True, None))
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/py_utils.py", line 387, in _single_map_nested
    mapped = [_single_map_nested((function, v, types, None, True, None)) for v in pbar]
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/py_utils.py", line 387, in <listcomp>
    mapped = [_single_map_nested((function, v, types, None, True, None)) for v in pbar]
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/py_utils.py", line 370, in _single_map_nested
    return function(data_struct)
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/download/download_manager.py", line 451, in _download
    out = cached_path(url_or_filename, download_config=download_config)
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/file_utils.py", line 188, in cached_path
    output_path = get_from_cache(
  File "/Users/xxx/miniconda3/envs/env/lib/python3.9/site-packages/datasets/utils/file_utils.py", line 570, in get_from_cache
    raise FileNotFoundError(f"Couldn't find file at {url}")
FileNotFoundError: Couldn't find file at https://huggingface.co/datasets/wentingzhao/anthropic-hh-first-prompt/resolve/11b393a5545f706a357ebcd4a5285d93db176715/cache1/downloads/87d66c365626feca116cba323c4856c9aae056e4503f09f23e34aa085eb9de15
```

However, seems it works fine for some datasets, for example, if works fine for `datasets.load_dataset("ag_news", cache_dir='cache2')["test"]`

But the dataset works fine for datasets==2.15.0, for example `pip install datasets==2.15.0`,
then

```python
import datasets

datasets.load_dataset("wentingzhao/anthropic-hh-first-prompt", cache_dir='cache3')["train"]

Dataset({
    features: ['user', 'system', 'source'],
    num_rows: 8552
})
```




### Expected behavior

2.16.0 should work as same as 2.15.0 for all datasets

### Environment info

python3.9
conda env
tested on MacOS and Linux