Issue: Failed to convert `string` with pyarrow for QED since 1.15.0

Comment:
Actually, re-opening this issue cause the error persists

```python
>>> load_dataset("qed")
Downloading and preparing dataset qed/qed (download: 13.43 MiB, generated: 9.70 MiB, post-processed: Unknown size, total: 23.14 MiB) to /home/victor_huggingface_co/.cache/huggingface/datasets/qed/qed/1.0.0/47d8b6f033393aa520a8402d4baf2d6bdc1b2fbde3dc156e595d2ef34caf7d75...
100%|███████████████████████████████████████████████████████████████████████| 2/2 [00:00<00:00, 2228.64it/s]
Traceback (most recent call last):       
  File "<stdin>", line 1, in <module>
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/load.py", line 1669, in load_dataset
    use_auth_token=use_auth_token,
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/builder.py", line 594, in download_and_prepare
    dl_manager=dl_manager, verify_infos=verify_infos, **download_and_prepare_kwargs
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/builder.py", line 681, in _download_and_prepare
    self._prepare_split(split_generator, **prepare_split_kwargs)
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/builder.py", line 1083, in _prepare_split
    num_examples, num_bytes = writer.finalize()
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/arrow_writer.py", line 468, in finalize
    self.write_examples_on_file()
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/arrow_writer.py", line 339, in write_examples_on_file
    pa_array = pa.array(typed_sequence)
  File "pyarrow/array.pxi", line 229, in pyarrow.lib.array
  File "pyarrow/array.pxi", line 110, in pyarrow.lib._handle_arrow_array_protocol
  File "/home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages/datasets/arrow_writer.py", line 125, in __arrow_array__
    out = pa.array(cast_to_python_objects(self.data, only_1d_for_numpy=True), type=type)
  File "pyarrow/array.pxi", line 315, 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: Could not convert 'in' with type str: tried to convert to boolean
```

Environment (datasets and pyarrow):

```bash
(promptsource) victor_huggingface_co@victor-dev:~/promptsource$ datasets-cli env

Copy-and-paste the text below in your GitHub issue.

- `datasets` version: 1.16.1
- Platform: Linux-5.0.0-1020-gcp-x86_64-with-debian-buster-sid
- Python version: 3.7.11
- PyArrow version: 6.0.1
```
```bash
(promptsource) victor_huggingface_co@victor-dev:~/promptsource$ pip show pyarrow
Name: pyarrow
Version: 6.0.1
Summary: Python library for Apache Arrow
Home-page: https://arrow.apache.org/
Author: 
Author-email: 
License: Apache License, Version 2.0
Location: /home/victor_huggingface_co/miniconda3/envs/promptsource/lib/python3.7/site-packages
Requires: numpy
Required-by: streamlit, datasets
```