Merge branch 'update-redis-ha-docs' into 'master'

Update recommended redis HA gitlab.rb

Closes omnibus-gitlab#4706

See merge request gitlab-org/gitlab!21348

doc/administration/high_availability/redis.md

@@ -71,7 +71,7 @@ Omnibus:
    redis['port'] = 6379
    redis['password'] = 'SECRET_PASSWORD_HERE'
 
-   gitlab_rails['auto_migrate'] = false
+   gitlab_rails['enable'] = false
    ```
 
 1. [Reconfigure Omnibus GitLab][reconfigure] for the changes to take effect.