Fix wrapped transformer config access in Flux2 Klein training

[tcaimm]

What does this PR do?

This PR fixes wrapped transformer config access in the Flux2 Klein DreamBooth LoRA training scripts.

When the transformer is wrapped by Accelerate, DDP, or FSDP, accessing transformer.config.guidance_embeds directly may not reliably read from the underlying model. This change uses unwrap_model(transformer).config.guidance_embeds instead, so guidance config is always read from the actual transformer module.

The fix is applied to:

• examples/dreambooth/train_dreambooth_lora_flux2_klein.py
• examples/dreambooth/train_dreambooth_lora_flux2_klein_img2img.py

Fixes # (issue)

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Who can review?

@sayakpaul

[sayakpaul]

Thanks!