Fix bnb training test failure
Author: matthewdouglas
Pull request: yes
Labels: name: Tests

# What does this PR do?

Fixes a test failure that resulted from the introduction of `OPTSdpaAttention` as the default implementation in #33298. Discussed internally on Slack.

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## Who can review?

@BenjaminBossan @SunMarc 

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_34414). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

I saw that the issue was with the `OPTSdpaAttention` but why it doesn't work with it ? Any ideas ? cc @matthewdouglas 

The issue was that the old check `"OPTAttention" in repr(type(module))` didn't match any layer anymore, hence no LoRA layers were added, hence no trainable parameters were found, resulting in the error.

Oh, I read the PR too fast. Thanks ! It makes sense now