minor #20551 [Validator] [CustomValidationConstraint] Fix wrong attribute class name (cavasinf)

This PR was merged into the 6.4 branch.

Discussion
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[Validator] [CustomValidationConstraint] Fix wrong attribute class name

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Commits
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cf778c0 Update custom_constraint.rst

Author: javiereguiluz

validation/custom_constraint.rst

@@ -499,7 +499,7 @@ A class constraint validator must be applied to the class itself:
 
         use App\Validator as AcmeAssert;
 
-        #[AcmeAssert\ProtocolClass]
+        #[AcmeAssert\ConfirmedPaymentReceipt]
         class AcmeEntity
         {
             // ...