Corrected spelling errors in README_ko.md
Author: yusha-g
Pull request: yes

1. 독립적이여서 to 독립적 이어서
2. 마스킹된 to 마스킹 된
3. 파이썬 to 파이선

# What does this PR do?
Fixed typos and spelling mistakes
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Fixes # (issue)


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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_19816). All of your documentation changes will be reflected on that endpoint.

@eunseojo could you give a quick look?