Fix show/hide discussion link

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/views/projects/notes/_discussion.html.haml

 - note = discussion_notes.first
-.discussion.js-details-container.js-toggler-container.open{ class: note.discussion_id }
+.discussion.js-toggle-container{ class: note.discussion_id }
   .discussion-header
     .discussion-actions
-      = link_to "javascript:;", class: "js-details-target turn-on js-toggler-target" do
-        %i.icon-eye-close
-        Hide discussion
-      = link_to "javascript:;", class: "js-details-target turn-off js-toggler-target" do
-        %i.icon-eye-open
-        Show discussion
+      = link_to "#", class: "js-toggle-button" do
+        %i.icon-chevron-up
+        Show/hide discussion
     = image_tag avatar_icon(note.author_email), class: "avatar s32"
     %div
       = link_to_member(@project, note.author, avatar: false)
@@ -33,7 +30,7 @@
       = link_to_member(@project, last_note.author, avatar: false)
       %span.discussion-last-update
         #{time_ago_with_tooltip(last_note.updated_at, 'bottom', 'discussion_updated_ago')}
-  .discussion-body
+  .discussion-body.js-toggle-content
     - if note.for_diff_line?
       - if note.active?
         = render "projects/notes/discussion_diff", discussion_notes: discussion_notes, note: note
@@ -47,11 +44,3 @@
       .notes{ rel: discussion_notes.first.discussion_id }
         = render discussion_notes
       = render "projects/notes/discussion_reply_button", note: discussion_notes.first
-
-    -# will be shown when the other one is hidden
-    .discussion-hidden.content.hide
-      .note
-        %em Hidden discussion.
-        = link_to "javascript:;", class: "js-details-target js-toggler-target" do
-          %i.icon-eye-open
-          Show