Core/Grid: Code cleanup

Remove unused method that should not be used anyway

src/server/game/Grids/NGrid.h

@@ -92,7 +92,6 @@ class NGrid
         }
 
         uint32 GetGridId(void) const { return i_gridId; }
-        void SetGridId(const uint32 id) const { i_gridId = id; }
         grid_state_t GetGridState(void) const { return i_cellstate; }
         void SetGridState(grid_state_t s) { i_cellstate = s; }
         int32 getX() const { return i_x; }