upgrade OS on connection broker

Hi guys,

i have 2 connection broker server with 2012 R2 configured on ha mode. So i need to upgrade this server to 2019 because i will need to use 2019 as host server.

i have saw this document

https://docs.microsoft.com/en-us/windows-server/remote/remote-desktop-services/upgrade-to-rds#flow-for-deployment-upgrades 

but it's not clear, i need  remove the server from HA group, upgrade OS, after upgrade the second server without remove the HA group and finally add the first server to HA group again? it's the correct procedure? 

thanks

Andrea