Add missing QTreeWidget::dropEvent to d'n'd atempt occuring in same location.

Remove 'Overwrite attempt' dialog as obsolete. Now moving item, e.g. from folder to same folder, will just make it the last child of the folder.

src/rss/feedlistwidget.cpp

@@ -205,7 +205,7 @@ void FeedListWidget::dropEvent(QDropEvent *event) {
   foreach (QTreeWidgetItem *src_item, src_items) {
     RssFilePtr file = getRSSItem(src_item);
     if (dest_folder->hasChild(file->id())) {
-      emit overwriteAttempt(file->id());
+      QTreeWidget::dropEvent(event);
       return;
     }
   }