[Doctrine] Update doctrine.rst

As the type hinting from setter is available, this example will not work.

Even without `declare(strict_types=1);` string which could be convert to integer will work but with it, impossible to run this example, as we will have the error "int" expected.

Author: chadyred

doctrine.rst

@@ -448,12 +448,6 @@ Consider the following controller code::
         public function createProduct(ValidatorInterface $validator): Response
         {
             $product = new Product();
-            // This will trigger an error: the column isn't nullable in the database
-            $product->setName(null);
-            // This will trigger a type mismatch error: an integer is expected
-            $product->setPrice('1999');
-
-            // ...
 
             $errors = $validator->validate($product);
             if (count($errors) > 0) {