Use the readiness check instead of the sign_in page for LB health checks

doc/install/aws/manual_install_aws.md

@@ -268,8 +268,7 @@ On the EC2 dashboard, look for Load Balancer in the left navigation bar:
 1. Click **Configure Health Check** and set up a health check for your EC2 instances.
    1. For **Ping Protocol**, select HTTP.
    1. For **Ping Port**, enter 80.
-   1. For **Ping Path**, enter `/users/sign_in`. (We use `/users/sign_in` as it's a public endpoint that does
-   not require authentication.)
+   1. For **Ping Path** - we recommend that you [use the Readiness check endpoint](../../administration/load_balancer.md#readiness-check). You'll need to add [the VPC IP Adddress Range (CIDR)](https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-security-groups.html#elb-vpc-nacl) to the [IP Allowlist](../../administration/monitoring/ip_whitelist.md) for the [Health Check endpoints](../../user/admin_area/monitoring/health_check.md)
    1. Keep the default **Advanced Details** or adjust them according to your needs.
 1. Click **Add EC2 Instances** - don't add anything as we will create an Auto Scaling Group later to manage instances for us.
 1. Click **Add Tags** and add any tags you need.