🌐 [i18n-KO] Translated model_doc/bert.md to Korean

[boyunJang]

What does this PR do?

Translated the model_doc/bert.md file of the documentation to Korean.
Thank you in advance for your review.

Part of #20179

Before reviewing

• Check for missing / redundant translations (번역 누락/중복 검사)
• Grammar Check (맞춤법 검사)
• Review or Add new terms to glossary (용어 확인 및 추가)
• Check Inline TOC (e.g. [[lowercased-header]])
• Check live-preview for gotchas (live-preview로 정상작동 확인)

Who can review? (Initial)

May you please review this PR?

@junejae, @Jwaminju, @010kim, @4N3MONE, @boyunJang

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,
  Pull Request section?
• 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? (Final)

[4N3MONE]

Suggested change

	- BERT는 절대적 위치 임베딩을 사용하는 모델이므로 입력을 왼쪽이 아닌 오른쪽에서 패딩하는 것이 일반적으로 권장됩니다.
	- BERT는 절대적 위치 임베딩을 사용하는 모델이므로 입력을 왼쪽이 아닌 오른쪽에서 패딩하는 것을 일반적으로 권장합니다.

자연스러운 문장으로 수정해 보았습니다.