[train_dreambooth_flux] Add LANCZOS as the default interpolation mode for image resizing

[ishandutta0098]

What does this PR do?

This PR will add LANCZOS as a default interpolation mode for the image resizing in the training script for dreambooth flux and if the users prefers they can choose BILINEAR.

Fixes #11390

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@asomoza

[linoytsaban]

Thanks @ishandutta0098!

[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!