minor #10810 [Validator] Explained how to use array constant in annotation (nikophil)

This PR was squashed before being merged into the 3.4 branch (closes #10810).

Discussion
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[Validator] Explained how to use array constant in annotation

Hi,

few days ago i tried to add a new feature to the `choice` validator constraint, by adding a new `choicesFromConstant` option.
symfony/symfony#29658
But then, i realized this was already supported.

I think this should be documented, as i think a lot of people don't know this feature.

thanks.

Commits
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7774aab [Validator] Explained how to use array constant in annotation

Author: javiereguiluz

reference/constraints/Choice.rst

@@ -47,13 +47,17 @@ If your valid choice list is simple, you can pass them in directly via the
 
         class Author
         {
+            const GENRES = ['fiction', 'non-fiction'];
+
             /**
              * @Assert\Choice({"New York", "Berlin", "Tokyo"})
              */
             protected $city;
 
             /**
-             * @Assert\Choice(choices={"fiction", "non-fiction"}, message="Choose a valid genre.")
+             * You can also directly provide an array constant to the "choices" option in the annotation
+             *
+             * @Assert\Choice(choices=Author::GENRES, message="Choose a valid genre.")
              */
             protected $genre;
         }
@@ -211,7 +215,7 @@ constraint.
             }
         }
 
-If the callback is stored in a different class and is static, for example ``AppBundle\Entity\Genre``,
+If the callback is defined in a different class and is static, for example ``AppBundle\Entity\Genre``,
 you can pass the class name and the method as an array.
 
 .. configuration-block::