Remove mention of ssh:// URLs from repository mirroring instructions

app/views/projects/mirrors/_instructions.html.haml

 .account-well.prepend-top-default.append-bottom-default
   %ul
     %li
-      The repository must be accessible over <code>http://</code>, <code>https://</code>, <code>ssh://</code> or <code>git://</code>.
+      The repository must be accessible over <code>http://</code>, <code>https://</code> or <code>git://</code>.
     %li
       If your HTTP repository is not publicly accessible, add authentication information to the URL: <code>https://username:password@gitlab.company.com/group/project.git</code>.
-    %li
-      If your SSH repository is not publicly accessible, add the public SSH key of the GitLab server to the remote repository.
     %li
       The update action will time out after 10 minutes. For big repositories, use a clone/push combination.