minor #13990 [Validator] Made the code sample more explicit with accepted values (lyrixx)

This PR was merged into the 3.4 branch.

Discussion
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[Validator] Made the code sample more explicit with accepted values

I'm not sure, I did not tested it, but it looks like the previous code sample was wrong

Commits
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dfaa5f2 [Validator] Made the code sample more explicit with accepted values

Author: xabbuh

reference/constraints/Collection.rst

@@ -207,7 +207,7 @@ you can do the following:
              *     }
              * )
              */
-            protected $profileData = ['personal_email'];
+            protected $profileData = ['personal_email' => 'email@example.com'];
         }
 
     .. code-block:: yaml