Update to work using Llama 3
# What does this PR do ?

fix the script to convert llama3 from nemo to hf format.
![image](https://github.com/NVIDIA/NeMo/assets/27715376/ab24e8b4-95cf-4e31-bb56-c60a6516cf6d)




# Changelog 
- Stop using LlamaTokenizer and start using AutoTokenizer from Transformers.

# Usage
```python
python3 NeMo/scripts/checkpoint_converters/convert_llama_nemo_to_hf.py \
    --input_name_or_path llama3-8b.nemo \
    --output_path llama3-8b-hf/pytorch_model.bin \
    --hf_input_path Meta-Llama-3-8B \
    --hf_output_path llama3-8b-hf \
    --input_tokenizer Meta-Llama-3-8B \
    --hf_output_tokenizer llama3-8b-hf
```
you must except something like this when the script finishes:
![image](https://github.com/NVIDIA/NeMo/assets/27715376/1093b660-4b8a-460e-b6b2-9065c55ba2de)


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# Additional Information
* there is an issue in hf related but is not the same script https://huggingface.co/meta-llama/Meta-Llama-3-8B-Instruct/discussions/37
