Remove wrong model_args supplied
# What does this PR do?

`PretrainedConfig.from_pretrained` method doesn't accept positional arguments, while the `PreTrainedModel.from_pretrained` supplies `model_args` as positional arguments to it when a config is not provided.

## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@LysandreJik @sgugger 
The failure seems not related to this PR.<|||||>@sgugger Fixed, thanks for pointing it out.<|||||>There seems to be an issue with the code quality issues! Do you mind fixing these by running the following at the root of your clone?

```
pip install -e .[quality]
make fixup
```<|||||>@LysandreJik the tests are passing. Let's merge it?<|||||>Thanks again!