remove "instanceof Pawn"

app/src/main/java/chess/model/Game.java

@@ -1,6 +1,6 @@
 package chess.model;
 
-import chess.model.pieces.Pawn;
+import chess.model.visitor.PawnIdentifier;
 
 public class Game {
 	private final ChessBoard board;
@@ -66,15 +66,15 @@ public class Game {
 	 */
 	private Coordinate pawnPromotePosition(Color color) {
 		int enemyLineY = color == Color.White ? 0 : 7;
+		PawnIdentifier identifier = new PawnIdentifier(color);
 
 		for (int x = 0; x < Coordinate.VALUE_MAX; x++) {
 			Coordinate pieceCoords = new Coordinate(x, enemyLineY);
 			Piece piece = getBoard().pieceAt(pieceCoords);
 
-			if (piece == null || !(piece instanceof Pawn) || piece.getColor() != color)
-				continue;
+			if (identifier.isPawn(piece))
+				return pieceCoords;
 
-			return pieceCoords;
 		}
 
 		return null;