Hide button on mobile

app/views/projects/diffs/_diffs.html.haml

@@ -8,9 +8,9 @@
   .inline-parallel-buttons
     - if show_whitespace_toggle
       - if current_controller?(:commit)
-        = commit_diff_whitespace_link(@project, @commit)
+        = commit_diff_whitespace_link(@project, @commit, class: 'hidden-xs')
       - elsif current_controller?(:merge_requests)
-        = diff_merge_request_whitespace_link(@project, @merge_request)
+        = diff_merge_request_whitespace_link(@project, @merge_request, class: 'hidden-xs')
     .btn-group
       = inline_diff_btn
       = parallel_diff_btn