Merge branch 'docs-aws-update-requirements' into 'master'

Add SSL certificate to Requirements

See merge request gitlab-org/gitlab!26277

doc/install/aws/index.md

@@ -33,6 +33,9 @@ In addition to having a basic familiarity with [AWS](https://docs.aws.amazon.com
 - [To create or upload an SSH key](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-key-pairs.html)
   to connect to the instance via SSH
 - A domain name for the GitLab instance
+- An SSL/TLS certificate to secure your domain. If you do not already own one, you can provision a free public SSL/TLS certificate through [AWS Certificate Manager](https://aws.amazon.com/certificate-manager/)(ACM) for use with the [Elastic Load Balancer](#load-balancer) we'll create.
+
+NOTE: **Note:** It can take a few hours to validate a certificate provisioned through ACM. To avoid delays later, request your certificate as soon as possible.
 
 ## Architecture