Improvement for k8s.io/zh/docs/concepts/policy/pod-security-policy/

[pacoxu]

This chinese version is not updated.

allowPrivilegeEscalation is not mentioned, and there are no examples for default psp

https://kubernetes.io/docs/concepts/policy/pod-security-policy/#privilege-escalation
https://kubernetes.io/zh/docs/concepts/policy/pod-security-policy/

[sftim]

/language zh
/kind cleanup

[ydcool]

WIP k8smeetup/website-tasks#3496

[ydcool]

/assign @ydcool

[tanjunchen]

@ydcool
any progress?

[ydcool]

@tanjunchen Sorry for the long delay... finally pushed.