fix formatting of detail block

Author: crichID

responses/02_repo-owner-answer.md

@@ -5,15 +5,16 @@ A repository _does_ exist at githubtraining/training-manual, but it is private.
 ![gif of repository, pointing to ownership by githubtraining organization, and to a private visibility](https://user-images.githubusercontent.com/6351798/56159957-32413700-5f83-11e9-90f6-c1b64ade39c4.gif)
 
 <details>
-<summary>Why can't you see it then? Review the <b>Files Changed</b> tab and see if you can figure it out. Collapse this text if you'd like an explanation.</summary>
+<summary>Why can't you see it then? Review the <b>Files Changed</b> tab and see if you can figure it out. Expand this text if you'd like an explanation.</summary>
+
+## Understanding repository visibility
 
 The repository `training-manual` in the @githubtraining organization is private. There are three types of repository visiility: public, internal, and private. Our repository, `githubtraining/training-manual`, isn't public. It could be internal, which means only members of the organizations that an account owns will see it, or it could be private, which means only teams and individuals that have been granted access to it can see it. Otherwise, it'll appear like the repository doesn't exist to you. This is an example of why having the right ownership structure is important. Having too many organizations with restrictive permissions silos and isolates each organization's work.
-</summary>
 
 Here are some recommendations based on some :sparkles: use of GitHub that we've seen:
 - Use the internal visibility (currently in beta) if you're working on behalf of an account with multiple organizations
 - Name your repositories in a meaningful manner. Usually a simple project or application name will suffice.
-</summary>
+<hr>
 </details>
 
 Please merge this pull request.