🌐 [i18n-KO] Translated main_classes/callback.md to Korean (#33572)

* docs: ko: callback.md

* feat: nmt draft & manual edits

* fix: resolve suggestions

* Update docs/source/ko/main_classes/callback.md

* Apply suggestions from code review

* Apply suggestions from code review

확인했습니다! 상세한 리뷰 정말 감사합니다!

Co-authored-by: boyunJang <gobook1234@naver.com>

* Update _toctree.yml

Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

---------

Co-authored-by: boyunJang <gobook1234@naver.com>
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>

docs/source/ko/_toctree.yml

@@ -276,8 +276,8 @@
       title: 자동 클래스
     - local: in_translation
       title: (번역중) Backbones
-    - local: in_translation
-      title: (번역중) Callbacks
+    - local: main_classes/callback
+      title: 콜백
     - local: main_classes/configuration
       title: 구성
     - local: main_classes/data_collator