[docstring] Fix docstring for ErnieConfig, ErnieMConfig
Author: Sparty
Pull request: yes

# What does this PR do?

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Fixes https://github.com/huggingface/transformers/issues/26638


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?


## Who can review?

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Models:

- text models: @ArthurZucker and @younesbelkada
- vision models: @amyeroberts
- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
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Documentation: @stevhliu and @MKhalusova

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Comments:
Feel free to ping @ydshieh when this is ready for a review! 

@Sparty Once ready for a review, could you remove the Draft mode. Thanks

I removed the draft mode. Thank you @ydshieh and @ArthurZucker 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_27029). All of your documentation changes will be reflected on that endpoint.

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.

I'd want to merge, but we need this to be rebased @Sparty if you can run something like `git pull upstream main` and push 🤗 

I have rebased. @ydshieh @ArthurZucker Could you merge this?

Thank you 🤗