Fix flax whisper tokenizer bug

[hannan72]

What does this PR do?

Fixes Bug when using whisper tokenizer for flax whisper model, according to the issue #32936

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [ ] Did you read the contributor guideline, Pull Request section?
• [ ] Was this discussed/approved via a Github issue or the forum? Please add a link to it if that's the case.
• [ ] Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings.
• [ ] Did you write any new necessary tests?

Who can review?

@ArthurZucker @sanchit-gandhi

Models:

• text models: @ArthurZucker
• vision models: @amyeroberts
• speech models: @sanchit-gandhi
• graph models: @clefourrier

Library:

• flax: @sanchit-gandhi
• generate: @zucchini-nlp (visual-language models) or @gante (all others)
• pipelines: @Narsil
• tensorflow: @gante and @Rocketknight1
• tokenizers: @ArthurZucker
• trainer: @muellerzr and @SunMarc

Integrations:

• deepspeed: HF Trainer/Accelerate: @muellerzr
• ray/raytune: @richardliaw, @amogkam
• Big Model Inference: @SunMarc
• quantization (bitsandbytes, autogpt): @SunMarc

Documentation: @stevhliu

HF projects:

• accelerate: different repo
• datasets: different repo
• diffusers: different repo
• rust tokenizers: different repo

Maintained examples (not research project or legacy):

• Flax: @sanchit-gandhi
• PyTorch: See Models above and tag the person corresponding to the modality of the example.
• TensorFlow: @Rocketknight1

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