Indeed, there is no update information. You have to do it manually.
I just figured out how:
1/ Take a backup of your configuration
2/ Uninstall Zigbee2MQTT
3/ Re-install it (click on the 3 dots in Supervisor -> Add-ons -> Respositories and enter https://github.com/zigbee2mqtt/hassio-zigbee2mqtt)
4/ Then re-install
5/ ‘Re-load’ your existing configuration
The above steps worked for me, hopefully also for you.
All existing, joined devices, will still work after the upgrade.
Success