升级到 18.04.5 后仍显示“新版本‘18.04.5 LTS’可用。”消息

Question

我刚刚用命令将 ubuntu 16.xx(16.04 或 16.10) 升级到 18.04 sudo do-release-upgrade。欢迎消息显示我已升级到18.04.5，但“有新版本可用”消息仍然保留。

Welcome to Ubuntu 18.04.5 LTS (GNU/Linux 4.4.0-209-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage
New release '18.04.5 LTS' available.
Run 'do-release-upgrade' to upgrade to it.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.5 LTS
Release:        18.04
Codename:       bionic

我的升级失败了吗？如何检查我的系统是否升级成功？