Make tokenizer_path to be non-mandatory

[A9isha]

Description

Simplify the parameters for running on MaxText by removing tokenizer_path as a required argument.

FIXES: b/490520651

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Tests

Ran locally on a v5p-8 the following commands:

# With tokenizer path
python3 -m src.maxtext.trainers.post_train.rl.train_rl src/maxtext/configs/post_train/rl.yml   model_name=llama3.1-8b-Instruct   tokenizer_path=meta-llama/Llama-3.1-8B-Instruct   load_parameters_path=/path/to/checkpoint   run_name=maz-8b-$RANDOM   base_output_directory=/path/to/gcs/bucket   hf_access_token=<HF_TOKEN> dataset_name=gsm8k steps=4 rollout_tensor_parallelism=-1 rollout_data_parallelism=1 rollout_expert_parallelism=1

# Without tokenizer path
python3 -m src.maxtext.trainers.post_train.rl.train_rl src/maxtext/configs/post_train/rl.yml   model_name=llama3.1-8b-Instruct   tokenizer_path=meta-llama/Llama-3.1-8B-Instruct   load_parameters_path=/path/to/checkpoint   run_name=maz-8b-$RANDOM   base_output_directory=/path/to/gcs/bucket   hf_access_token=<HF_TOKEN> dataset_name=gsm8k steps=4 rollout_tensor_parallelism=-1 rollout_data_parallelism=1 rollout_expert_parallelism=1

Checklist

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• I have necessary comments in my code, particularly in hard-to-understand areas.
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• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.

[SurbhiJainUSC]

Can we do the similar change for SFT?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[A9isha]

Can we do the similar change for SFT?

Yes done now