Remove useless variable game.timerStartTime

It sometimes gets set to SDL_GetTicks(), but without being checked or
actually used, it's useless and does nothing.

desktop_version/src/Game.h

@@ -136,7 +136,6 @@ public:
     //public var crewstats:Array = new Array();
     int lastsaved;
     int deathcounts;
-    int timerStartTime;
 
     int frames, seconds, minutes, hours;
     bool gamesaved;