Remove Game::shouldreturntopausemenu

This kludge variable was used to re-set the warp background after coming
back from the in-game settings menus. But since #522 got merged, this
has no longer been necessary.

desktop_version/src/Game.h

@@ -433,7 +433,6 @@ public:
 
     bool ingame_titlemode;
 
-    bool shouldreturntopausemenu;
     void returntopausemenu();
     void unlockAchievement(const char *name);