Remove unused variable Game::menuselection

I presume it was meant to have the text of the currently-selected menu
option inside it, before the code switched over to using the indice of
the currently-selected menu instead? Would've been more error-prone to
use the text name directly.

desktop_version/src/Game.h

@@ -221,7 +221,6 @@ public:
     //Main Menu Variables
     std::vector<MenuOption> menuoptions;
     int currentmenuoption ;
-    std::string menuselection;
     enum Menu::MenuName currentmenuname, previousmenuname;
     int current_credits_list_index;
     int menuxoff, menuyoff;