Fix typo
Author: susnato
Pull request: yes

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This PR changes all `lenght` to `length`

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Comments:
Thanks for this PR @susnato . Would you like to find/replace all occurrences of `lenght` in the codebase? Thank you!

Hi @ydshieh , I have changed all occurrences of `lenght` to `length`. 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_25966). All of your documentation changes will be reflected on that endpoint.