Make car2 a type of Car instead of ConvertibleCar (#48495)

Author: BartoszKlonowski

docs/csharp/programming-guide/classes-and-structs/knowing-when-to-use-override-and-new-keywords.md

@@ -279,7 +279,7 @@ public static void TestCars1()
     // used in the definition of ShowDetails in the ConvertibleCar  
     // class.
   
-    ConvertibleCar car2 = new ConvertibleCar();  
+    Car car2 = new ConvertibleCar();  
     car2.DescribeCar();  
     System.Console.WriteLine("----------");