LogWindow: don't unconfigure logger on destruction

This was causing Dolphin to always save "WriteToWindow = False". Instead
of disabling logging to the window (a config value), tell LogManager
that there's no window to log to (a runtime state).

Source/Core/DolphinWX/LogWindow.h

@@ -46,7 +46,6 @@ private:
   LogManager* m_LogManager;
   std::queue<std::pair<u8, wxString>> msgQueue;
   bool m_LogAccess;
-  bool m_has_listeners = true;
 
   // Controls
   wxBoxSizer* sBottom;