Add datasets to the requirements for Stable Diffusion training

[yafshar]

What does this PR do?

• Add a missing datasets to the requirements for Stable Diffusion training

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

[yafshar]

@regisss this is a minor missing requirements

>>> ~/optimum-habana/examples/stable-diffusion/training# python train_dreambooth_lora_flux.py     --pretrained_model_name_or_path="black-forest-labs/FLUX.1-dev"     --dataset="dog"     --prompt="a photo of sks dog"     --output_dir="dog_lora_flux"     --mixed_precision="bf16"     --weighting_scheme="none"     --resolution=1024     --train_batch_size=1     --learning_rate=1e-4     --guidance_scale=1     --report_to="tensorboard"     --gradient_accumulation_steps=4     --gradient_checkpointing     --lr_scheduler="constant"     --lr_warmup_steps=0     --cache_latents     --rank=4     --max_train_steps=500     --seed="0"     --use_hpu_graphs_for_inference     --use_hpu_graphs_for_training     --gaudi_config_name="Habana/stable-diffusion"

Traceback (most recent call last):
  File "/root/optimum-habana/examples/stable-diffusion/training/train_dreambooth_lora_flux.py", line 39, in <module>
    from datasets import load_dataset
ModuleNotFoundError: No module named 'datasets'

[HuggingFaceDocBuilderDev]

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[regisss]

LGTM!