Update modeling_gpt2.py
Author: nikitakapitan
Pull request: yes

Changed the declaration order in __ init __ so it is aligned with operational order.

As consequence, __ repr __ method is now also aligned with operational order

# What does this PR do?

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Comments:
cc @ArthurZucker 

Can you just run `make style`, maybe it will put it back? 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_25150). All of your documentation changes will be reflected on that endpoint.

Is there anything I can do to help merging it? 

You will need to fix the tests. As you can see from the failing check, the models that copy GPT-2 need to be updated with this change, so you need to run `make fix-copies`.

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.