Fix multiplayer dropdowns and proxy model

* Filters in the lobby properly remove rooms
* Multiplayer menu items for Show Room and Leave Room work as intended

src/citra_qt/main.h

@@ -12,7 +12,6 @@
 #include "common/announce_multiplayer_room.h"
 #include "core/core.h"
 #include "core/hle/service/am/am.h"
-#include "network/network.h"
 #include "ui_main.h"
 
 class AboutDialog;
@@ -55,7 +54,6 @@ class GMainWindow : public QMainWindow {
 public:
     void filterBarSetChecked(bool state);
     void UpdateUITheme();
-    void ChangeRoomState();
 
     GameList* game_list;
     GMainWindow();