[position] The KingMoveGenerator doesn't use push or capture masks

Mark these arguments with an _ so the linter stops complaining about it.

position/src/move_generator/king.rs

@@ -20,8 +20,8 @@ impl MoveGeneratorInternal for KingMoveGenerator {
     fn move_set_for_piece(
         position: &Position,
         placed_piece: PlacedPiece,
-        capture_mask: BitBoard,
-        push_mask: BitBoard,
+        _capture_mask: BitBoard,
+        _push_mask: BitBoard,
     ) -> MoveSet {
         let piece = placed_piece.piece();
         let color = piece.color();