[train_text_to_image_lora] Better image interpolation in training scripts follow up

[tongyu0924]

What does this PR do?

Fixes #11390

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[linoytsaban]

Thanks @tongyu0924!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[asomoza]

thanks!

[asomoza]

failing test are not related to this PR