Docs feedback: Make text less confusing for users that are not aware you can self-host

On the community forum we have seen several issues from people who have followed https://docs.gitlab.com/ee/user/ssh.html without being aware that they could host their own GitLab instance. They sometimes get confused by point 2 in the "Verify that you can connect" section, because "your GitLab instance URL" doesn't mean anything to them. My suggestion would be the simple addition of "(if you use the SaaS offering, the instance URL is gitlab.com)".