Disable brew cask updater

hack/jenkins/release_update_brew.sh

@@ -39,6 +39,11 @@ if [ -z "${NEW_SHA256}" ]; then
   exit 1
 fi
 
+echo "***********************************************************************"
+echo "Sorry, this script has not yet been updated to support non-cask updates"
+echo "See https://github.com/kubernetes/minikube/issues/5779"
+echo "***********************************************************************"
+
 git config --global user.name "${GITHUB_USER}"
 git config --global user.email "${GITHUB_USER}@google.com"