Changed to filter out oddball list sizes
Author: spanglies
Pull request: yes

This PR fixes the issue of lists occasionally being of different sizes before being sent to `trainer.py`

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Fixes #18167


## Before submitting
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@sgugger My apologies for the third ping in a week. I believe I found a solution that would be more acceptable.

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_18248). All of your documentation changes will be reflected on that endpoint.

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