Tenth Korean l10n work for release 1.18

- Translate concepts/extend-kubenetes/service-catalog.md in Korean (#23233)
- Translate concepts/configuration/secret.md into Korean (#23110)
- Translate tasks/extend-kubernetes/setup-extension-api-server.md into … (#22574)
- Update outdated files in dev-1.18-ko.10 branch (#23013)

Co-authored-by: Seokho Son <shsongist@gmail.com>
Co-authored-by: Jerry Park <jaehwa@gmail.com>
Co-authored-by: santachopa <santachopa@naver.com>

content/ko/docs/concepts/services-networking/network-policies.md

@@ -4,8 +4,6 @@ content_type: concept
 weight: 50
 ---
 
-{{< toc >}}
-
 <!-- overview -->
 네트워크 정책은 {{< glossary_tooltip text="파드" term_id="pod">}} 그룹이 서로 간에 또는 다른 네트워크 엔드포인트와 통신할 수 있도록 허용하는 방법에 대한 명세이다.