Fix AttributeError in train_dreambooth_lora_flux2_img2img validation

[Ricardo-M-L]

What does this PR do?

Fixes an AttributeError in examples/dreambooth/train_dreambooth_lora_flux2_img2img.py that makes the validation flow unusable.

The validation block references args.validation_image_path:

if args.validation_prompt is not None:
    validation_image = load_image(args.validation_image_path).convert(\"RGB\")

But the CLI argument is defined as --validation_image:

parser.add_argument(
    \"--validation_image\",
    type=str,
    default=None,
    help=\"path to an image that is used during validation as the condition image ...\",
)

Argparse stores it as args.validation_image, so accessing args.validation_image_path raises AttributeError: 'Namespace' object has no attribute 'validation_image_path' the moment a user passes --validation_prompt, before any training actually starts.

Sibling scripts like train_dreambooth_lora_flux2_klein_img2img.py (L1437) and train_dreambooth_lora_flux_kontext.py already use the correct args.validation_image; this aligns this script with them.

Fixes

-        validation_image = load_image(args.validation_image_path).convert(\"RGB\")
+        validation_image = load_image(args.validation_image).convert(\"RGB\")

Before submitting

• This PR fixes a typo or improves the docs.
• Did you read the contributor guideline?

Who can review?

@sayakpaul @linoytsaban