Update audiobookshelf.sh

tweak

ct/audiobookshelf.sh

@@ -52,11 +52,8 @@ function default_settings() {
 
 function update_script() {
 header_info
-if [[ ! -d /var ]]; then msg_error "No ${APP} Installation Found!"; exit; fi
-msg_info "Updating $APP LXC"
-apt-get update &>/dev/null
-apt-get -y upgrade &>/dev/null
-msg_ok "Updated $APP LXC"
+if [[ ! -f /etc/apt/trusted.gpg.d/audiobookshelf-ppa.asc ]]; then msg_error "No ${APP} Installation Found!"; exit; fi
+echo "This application receives updates through the APT package manager."
 exit
 }