Remove extra css class markdown-area which prevented attachments upload.

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

@@ -46,7 +46,7 @@
         .note-edit-form
           = form_for note, url: project_note_path(@project, note), method: :put, remote: true, authenticity_token: true do |f|
             = render layout: 'projects/md_preview' do
-              = f.text_area :note, class: 'note_text js-note-text markdown-area js-gfm-input turn-on'
+              = f.text_area :note, class: 'note_text js-note-text js-gfm-input turn-on'
 
             .form-actions.clearfix
               = f.submit 'Save changes', class: "btn btn-primary btn-save js-comment-button"