MovePicker: retire per square MVV/LVA ordering

Is not used anyway and in case we need it again we
can resurrect from git archives.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/movepick.h

@@ -80,8 +80,7 @@ private:
   void score_evasions();
   void score_qcaptures();
   Move pick_move_from_list();
-  int find_best_index();
-  int find_best_index(Bitboard* squares, int values[]);
+  int find_best_index() const;
 
   const Position& pos;
   Move ttMove, mateKiller, killer1, killer2;