[zh] Fix task list

We now seem to have two sections on extending Kubernetes. This turns out
to be a folder name change problem after a closer investigation. The
English folder changed 'access-kubernetes-api' to 'extend-kubernetes',
but this change was not propagated to Chinese localization.

content/zh/docs/tasks/access-kubernetes-api/_index.md

@@ -1,4 +0,0 @@
----
-title: "扩展 Kubernetes"
-weight: 90
----

content/zh/docs/tasks/extend-kubernetes/_index.md

@@ -0,0 +1,5 @@
+---
+title: "扩展 Kubernetes"
+description: 了解针对工作环境需要来调整 Kubernetes 集群的进阶方法
+weight: 90
+---