Remove root directory name from index of wikis

app/views/projects/wikis/_wiki_pages.html.haml

+- wiki_pages.each do |wiki_page|
+  %li
+    = link_to wiki_page.title, namespace_project_wiki_path(@project.namespace, @project, wiki_page)
+    %small (#{wiki_page.format})
+    .pull-right
+      %small Last edited #{time_ago_with_tooltip(wiki_page.commit.authored_date)}

app/views/projects/wikis/pages.html.haml

@@ -15,13 +15,12 @@
   %ul.content-list
     - @wiki_directories.each do |wiki_directory, wiki_pages|
-      %li
-        = wiki_directory
-        %ul
-        - wiki_pages.each do |wiki_page|
-          %li
-            = link_to wiki_page.title, namespace_project_wiki_path(@project.namespace, @project, wiki_page)
-            %small (#{wiki_page.format})
-            .pull-right
-              %small Last edited #{time_ago_with_tooltip(wiki_page.commit.authored_date)}
+      - if wiki_directory == '/'
+        = render 'wiki_pages', wiki_pages: wiki_pages
+      - else
+        %li
+          = wiki_directory
+          %ul
+            = render 'wiki_pages', wiki_pages: wiki_pages
+
   = paginate @wiki_pages, theme: 'gitlab'