Disable prefix tuning and limit llama adapter

[mreso]

What does this PR do?

This PR disables prefix tuning and limit llama_adapter to non-FSDP use case.

Fixes # (issue)
#359

Feature/Issue validation/testing

Please describe the tests that you ran to verify your changes and relevant result summary. Provide instructions so it can be reproduced.
Please also list any relevant details for your test configuration.

• pytest tests/test_finetuning.py
  Logs for Test A

====================================================================================================================================== test session starts =======================================================================================================================================
platform linux -- Python 3.11.8, pytest-8.1.1, pluggy-1.4.0
rootdir: /home/mreso/llama-recipes
configfile: pyproject.toml
plugins: anyio-4.3.0, mock-3.14.0
collected 9 items

tests/test_finetuning.py .........                                                                                                                                                                                                                                                         [100%]

======================================================================================================================================== warnings summary ========================================================================================================================================
../.conda/envs/llama3/lib/python3.11/site-packages/fire/core.py:59
  /home/mreso/.conda/envs/llama3/lib/python3.11/site-packages/fire/core.py:59: DeprecationWarning: 'pipes' is deprecated and slated for removal in Python 3.13
    import pipes

src/llama_recipes/utils/train_utils.py:9
  /home/mreso/llama-recipes/src/llama_recipes/utils/train_utils.py:9: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
    from pkg_resources import packaging

../.conda/envs/llama3/lib/python3.11/site-packages/torch/distributed/_shard/checkpoint/__init__.py:8
  /home/mreso/.conda/envs/llama3/lib/python3.11/site-packages/torch/distributed/_shard/checkpoint/__init__.py:8: DeprecationWarning: torch.distributed._shard.checkpoint will be deprecated, use torch.distributed.checkpoint instead
    warnings.warn(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
================================================================================================================================= 9 passed, 3 warnings in 3.77s ==================================================================================================================================

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