Fix AttributeError/TypeError in sana_sprint model-card save

[Ricardo-M-L]

What this PR does

train_sana_sprint_diffusers.py ends training (under --push_to_hub) with:

https://github.com/huggingface/diffusers/blob/main/examples/research_projects/sana/train_sana_sprint_diffusers.py#L1758-L1766

if args.push_to_hub:
    save_model_card(
        repo_id,
        images=images,
        base_model=args.pretrained_model_name_or_path,
        instance_prompt=args.instance_prompt,
        validation_prompt=args.validation_prompt,
        repo_folder=args.output_dir,
    )

But the script has neither:

1. --instance_prompt on the parser (grep confirms zero add_argument call for it). args.instance_prompt raises AttributeError: 'Namespace' object has no attribute 'instance_prompt' when the kwarg value is evaluated.
2. An instance_prompt parameter on save_model_card (line 217 accepts only repo_id, images, base_model, validation_prompt, repo_folder — no **kwargs). Even if the attribute existed, the call would fail with TypeError: save_model_card() got an unexpected keyword argument 'instance_prompt'.

Why this is a real bug

This fires at the tail end of training with --push_to_hub, after the model has been saved locally — losing the hub upload for anyone running the documented workflow.

It's a dreambooth-pattern copy-paste leftover: Sana Sprint is not a dreambooth-style trainer — it takes --validation_prompt, not instance prompts. instance_prompt appears exactly once in the whole file (at this call site) and is never referenced inside save_model_card.

Fix

Drop the stray kwarg:

 save_model_card(
     repo_id,
     images=images,
     base_model=args.pretrained_model_name_or_path,
-    instance_prompt=args.instance_prompt,
     validation_prompt=args.validation_prompt,
     repo_folder=args.output_dir,
 )

The remaining kwargs now match save_model_card's signature exactly.

Before submitting

• Did you read the contributor guideline?
• Was this discussed/approved via a Github issue or the forum? N/A — dead-on-push-to-hub crash.
• Did you make sure to update the documentation with your changes? N/A.
• Did you write any new necessary tests? N/A — restores working --push_to_hub path.

Who can review?

@sayakpaul