[position] Remove an unnecessary type annotation

position/src/position/builders/move_builder.rs

@@ -67,7 +67,7 @@ where
 
         let player = self.position.player_to_move();
 
-        let captured_piece: Option<PlacedPiece> = if mv.is_en_passant() {
+        let captured_piece = if mv.is_en_passant() {
             // En passant captures the pawn directly ahead (in the player's direction) of the en passant square.
             let capture_square = match player {
                 Color::White => to_square.neighbor(Direction::South),