NXD clone_panel: Remove SSH option completely

The default was switched to HTTP in the previous patch, but let's completely
remos SSH option - we support only HTTP for git fetch/push.

app/views/shared/_clone_panel.html.haml

 - project = project || @project
 .git-clone-holder.input-group
   .input-group-addon.git-protocols
-    .input-group-btn
+    -# no ssh clone - only http is supported
+    -# .input-group-btn
       %button{ |
         type: 'button', |
         class: "btn #{ 'active' if default_clone_protocol == 'ssh' }#{ ' has_tooltip' if current_user && current_user.require_ssh_key? }", |