text: Title: Incomplete list of operations for admission webhook
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  **What happened**:
  Working on other doc bugs, I went looking for what calls admission plugins.  I found four call sites for validating plugins, documented in https://github.com/kubernetes/website/issues/20673 .  They correspond to the verbs CONNECT, CREATE, DELETE, and UPDATE.  But only two of those verbs are documented at https://github.com/kubernetes/kubernetes/blob/863ce9726e0aa617f03332f42ff3cebb7abe8fc0/staging/src/k8s.io/api/admissionregistration/v1/types.go#L465
  
  **What you expected to happen**:
  
  **How to reproduce it (as minimally and precisely as possible)**:
  
  **Anything else we need to know?**:
  
  **Environment**:
  - Kubernetes version (use `kubectl version`):
  - Cloud provider or hardware configuration:
  - OS (e.g: `cat /etc/os-release`):
  - Kernel (e.g. `uname -a`):
  - Install tools:
  - Network plugin and version (if this is a network-related bug):
  - Others:
  