fix(kubectl): redirect stderr in completion generation

Fixes #11364

plugins/kubectl/kubectl.plugin.zsh

@@ -10,7 +10,7 @@ if [[ ! -f "$ZSH_CACHE_DIR/completions/_kubectl" ]]; then
   _comps[kubectl]=_kubectl
 fi
 
-kubectl completion zsh >| "$ZSH_CACHE_DIR/completions/_kubectl" &|
+kubectl completion zsh 2> /dev/null >| "$ZSH_CACHE_DIR/completions/_kubectl" &|
 
 # This command is used a LOT both below and in daily life
 alias k=kubectl