Fix return metadata checking logic

[Xqle]

What does this PR do?

As suggested in #42009 (comment), when return_metadata is in kwargs but set to False, metadata should be popped.

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Who can review?

@zucchini-nlp @yonigozlan @molbap

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: glm4v, qwen3_vl, smolvlm, video_llama_3

[zucchini-nlp]

Thanks

[HuggingFaceDocBuilderDev]

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