Chef Infra Server upgrade instructions are missing link to Chef-Backend upgrade page

[teknofire]

User Story

As a SysAdmin I would like to have instructions on how to upgrade my Chef Backend HA system to the latest version.

Description

With the EOL of the Chef DRBD HA solution, we removed the HA upgrade instructions from https://docs.chef.io/upgrade_server.html#high-availability and didn't add or keep instructions for how to upgrade users with Chef-Backend HA.

There is a separate page that includes those instructions here: https://docs.chef.io/upgrade_server_ha_v2.html that should be linked to from that section.

Chef Version

Chef-Backend all versions

Platform Version

<! Tell us which Operating System distribution and version you're running Chef on. >

Definition of Done

User can find instructions on how to upgrade Chef-Backend HA installations from both https://docs.chef.io/upgrade_server.html#high-availability and https://docs.chef.io/upgrade_server_ha_v2.html

Demo Script / Repro Steps