minikube: fix spelling (#9270)

plugins/minikube/minikube.plugin.zsh

 # Autocompletion for Minikube.
 #
 if (( $+commands[minikube] )); then
-    __MINICUBE_COMPLETION_FILE="${ZSH_CACHE_DIR}/minicube_completion"
+    __MINIKUBE_COMPLETION_FILE="${ZSH_CACHE_DIR}/minikube_completion"
 
-    if [[ ! -f $__MINICUBE_COMPLETION_FILE ]]; then
-        minikube completion zsh >! $__MINICUBE_COMPLETION_FILE
+    if [[ ! -f $__MINIKUBE_COMPLETION_FILE ]]; then
+        minikube completion zsh >! $__MINIKUBE_COMPLETION_FILE
     fi
 
-    [[ -f $__MINICUBE_COMPLETION_FILE ]] && source $__MINICUBE_COMPLETION_FILE
+    [[ -f $__MINIKUBE_COMPLETION_FILE ]] && source $__MINIKUBE_COMPLETION_FILE
 
-    unset __MINICUBE_COMPLETION_FILE
+    unset __MINIKUBE_COMPLETION_FILE
 fi