🌐 [i18n-KO] Translated custom_models.mdx to Korean (#22534)

docs: ko: translated `custom_models.mdx`

Co-authored-by: Wonhyeong Seo <wonhseo@kakao.com>
Co-authored-by: Gabriel Yang <gabrielwithhappy@gmail.com>
Co-authored-by: Jungnerd <46880056+jungnerd@users.noreply.github.com>

docs/source/ko/_toctree.yml

@@ -26,8 +26,8 @@
   - sections:
     - local: in_translation
       title: (번역중) Create a custom architecture
-    - local: in_translation
-      title: (번역중) Sharing custom models
+    - local: custom_models
+      title: 사용자 정의 모델 공유하기
     - local: in_translation
       title: (번역중) Train with a script
     - local: sagemaker