[board] Remove an unused local variable from pieces.rs

board/src/position/pieces.rs

@@ -55,8 +55,6 @@ impl<'a> Iterator for Pieces<'a> {
         }
 
         if let (Some(bitboard), Some(shape)) = (next_nonempty_bitboard, current_shape) {
-            let piece = Piece::new(self.color, shape);
-
             let mut square_iterator = bitboard.occupied_squares();
 
             let mut next_placed_piece: Option<PlacedPiece> = None;