Remove DVDInterface::ChangeDiscAsHost

There isn't much point in keeping this utility function around
now that RunAsCPUThread provides a simple way of running things
on the CPU thread.

Source/Core/DolphinQt2/GameList/GameList.cpp

@@ -417,7 +417,8 @@ void GameList::DeleteFile()
 
 void GameList::ChangeDisc()
 {
-  DVDInterface::ChangeDiscAsHost(GetSelectedGame()->GetFilePath().toStdString());
+  Core::RunAsCPUThread(
+      [this] { DVDInterface::ChangeDisc(GetSelectedGame()->GetFilePath().toStdString()); });
 }
 
 QSharedPointer<GameFile> GameList::GetSelectedGame() const