fix(llama): fix LlamaTokenzier
Author: ry-sun
Pull request: yes

# What does this PR do?

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Fixes #22742

- #22742

This PR removes an extra `sep` token in the sequence length calculation.

Ref:

https://github.com/huggingface/transformers/blob/7df1343292a9d75f1410cb37a99f423dcde15dae/src/transformers/models/llama/tokenization_llama.py#L178-L187

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Models:

- text models: @ArthurZucker and @younesbelkada
- vision models: @amyeroberts
- speech models: @sanchit-gandhi
- graph models: @clefourrier

Library:

- flax: @sanchit-gandhi
- generate: @gante
- pipelines: @Narsil
- tensorflow: @gante and @Rocketknight1
- tokenizers: @ArthurZucker
- trainer: @sgugger

Integrations:

- deepspeed: HF Trainer: @stas00, Accelerate: @pacman100
- ray/raytune: @richardliaw, @amogkam

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HF projects:

- accelerate: [different repo](https://github.com/huggingface/accelerate)
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- diffusers: [different repo](https://github.com/huggingface/diffusers)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Thanks for your quick review, I have re-run the CI tests. 🤗 @amyeroberts @ArthurZucker