Remove useless variable game.coins

It kept getting set to 0 and getting incremented sometimes, but without
it ever actually getting checked, it's a useless variable.

desktop_version/src/Entity.cpp

@@ -2498,7 +2498,6 @@ void entityclass::updateentities( int i )
             //wait for collision
             if (entities[i].state == 1)
             {
-                game.coins++;
                 music.playef(4);
                 collect[entities[i].para] = 1;