[doc] Fix Korean Controlnet Train doc

[flyxiv]

What does this PR do?

• Fixes Controlnet Korean document to make it in sync with the English one.

Details:

1. Irrelevant Header

---

This header translates to dataset that fills the circle, which doesn't match the context of the following paragraph, which explains about using other stable diffusion model versions that can be used(v1.4 and 2.1) and how to use custom datasets.

2. Paragraph Containing Other Stable Diffusion Model Options

Also, if we see the English version of the same part, the doc only mentions about using custom datasets.

---

So we need to delete the paragraph about other stable diffusion model options so that the doc is in sync with the English one.

Final version:

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Who can review?

@stevhliu and @sayakpaul

[stevhliu]

Thanks for your fix! 🤗

[HuggingFaceDocBuilderDev]

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