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- Update outdated files in dev-1.18-ko.10 branch (#23013)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/tasks/tools/install-kubectl.md

@@ -26,7 +26,7 @@ card:
 1. 다음 명령으로 최신 릴리스를 다운로드한다.
 
     ```
-    curl -LO https://storage.googleapis.com/kubernetes-release/release/`curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt`/bin/linux/amd64/kubectl
+    curl -LO "https://storage.googleapis.com/kubernetes-release/release/$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)/bin/linux/amd64/kubectl"
     ```
 
     특정 버전을 다운로드하려면, `$(curl -s https://storage.googleapis.com/kubernetes-release/release/stable.txt)` 명령 부분을 특정 버전으로 바꾼다.