[i18n-KO] Fix typo and update translation in ethical_guidelines.md

[braintrue]

What does this PR do?

Adds the Korean translation of the ethical_guidelines.md file under docs/source/ko/conceptual/.

This update improves accessibility for Korean developers and researchers by providing an accurate, up-to-date translation of the Diffusers ethical guidelines.
It aligns with Hugging Face’s commitment to open collaboration and responsible AI.

Fixes #9396

Before submitting

• This PR improves the documentation (Korean translation update).
• I read the contributor guideline.
• I read the philosophy doc.
• I have synced the translation with the latest English version.
• I proofread the Korean text for clarity and consistency.

Who can review?

@stevhliu (Docs)
@sayakpaul (General)

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🗒️ Additional Context

This PR is part of the ongoing Korean i18n improvement efforts in the Diffusers documentation.
Previously, some files under docs/source/ko were marked “in progress.”
This PR completes and updates one of those documents (ethical_guidelines.md) based on the latest English content.

[stevhliu]

Thanks for the update!

[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.