Fix barthez tokenizer
The barthez tokenizer should be put in the "no config tokenizer", as two tokenizers with the same configs can't be put together.

Running the [following code](https://github.com/huggingface/transformers/issues/9422#issuecomment-759327863) works now:

```py
from transformers import AutoTokenizer

barthez_tokenizer = AutoTokenizer.from_pretrained("moussaKam/barthez")
```