DolphinQt: Properly Delete (Some) Widgets

This is not every memory leak, just the ones that were obvious.

Source/Core/DolphinQt/Debugger/WatchWidget.cpp

@@ -327,6 +327,7 @@ void WatchWidget::OnSave()
 void WatchWidget::ShowContextMenu()
 {
   QMenu* menu = new QMenu(this);
+  menu->setAttribute(Qt::WA_DeleteOnClose, true);
 
   if (!m_table->selectedItems().empty())
   {