minor #15620 Replaced doctrine annotations with attributes (zspine)

This PR was merged into the 5.3 branch.

Discussion
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Replaced doctrine annotations with attributes

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Commits
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aa67a0f Replaced doctrine annotations with attributes

Author: javiereguiluz

reference/constraints/Traverse.rst

@@ -94,30 +94,27 @@ that all have constraints on their properties.
         // src/Entity/BookCollection.php
         namespace App\Entity;
 
+        use App\Entity\Book;
         use Doctrine\Common\Collections\ArrayCollection;
-        use Doctrine\Common\Collections\Collection
+        use Doctrine\Common\Collections\Collection;
         use Doctrine\ORM\Mapping as ORM;
         use Symfony\Component\Validator\Constraints as Assert;
 
-        /**
-         * @ORM\Entity
-         */
+        #[ORM\Entity]
         #[Assert\Traverse]
         class BookCollection implements \IteratorAggregate
         {
             /**
              * @var string
-             *
-             * @ORM\Column
              */
+            #[ORM\Column]
             #[Assert\NotBlank]
             protected $name = '';
 
             /**
              * @var Collection|Book[]
-             *
-             * @ORM\ManyToMany(targetEntity="App\Entity\Book")
              */
+            #[ORM\ManyToMany(targetEntity: Book::class)] 
             protected $books;
 
             // some other properties