fix: lazily import soundfile in datasets

[anubhutivyas]

What does this PR do ?

• We recently removed codecs and soundfile from RL image, refer in this PR - fix: remove python shim for already removed codec files NVIDIA-NeMo/nemo-platform#1415
• It caused DPO training to fail

Traceback (most recent call last):
  File "/app/services/rl/src/nmp/rl/tasks/training/backends/nemo_rl/dpo_driver.py", line 21, in <module>
    from nemo_rl.algorithms.dpo import MasterConfig, dpo_train, setup
  File "/opt/nemo-rl/nemo_rl/algorithms/dpo.py", line 31, in <module>
    from nemo_rl.data.datasets import AllTaskProcessedDataset
  File "/opt/nemo-rl/nemo_rl/data/datasets/__init__.py", line 15, in <module>
    from nemo_rl.data.datasets.eval_datasets import load_eval_dataset
  File "/opt/nemo-rl/nemo_rl/data/datasets/eval_datasets/__init__.py", line 15, in <module>
    from nemo_rl.data.datasets.eval_datasets.daily_omni import DailyOmniEvalDataset
  File "/opt/nemo-rl/nemo_rl/data/datasets/eval_datasets/daily_omni.py", line 20, in <module>
    from nemo_rl.data.datasets.response_datasets.daily_omni import DailyOmniDataset
  File "/opt/nemo-rl/nemo_rl/data/datasets/response_datasets/__init__.py", line 20, in <module>
    from nemo_rl.data.datasets.response_datasets.audiomcq import AudioMCQDataset
  File "/opt/nemo-rl/nemo_rl/data/datasets/response_datasets/audiomcq.py", line 20, in <module>
    import soundfile as sf
ModuleNotFoundError: No module named 'soundfile'

• Fix is to lazily import soundfile

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