minor #35816 [Validator] Remove specific check for Valid targets (ogi…

…zanagi)

This PR was merged into the 3.4 branch.

Discussion
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[Validator] Remove specific check for Valid targets

| Q             | A
| ------------- | ---
| Branch?       | 3.4 <!-- see below -->
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | N/A <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT
| Doc PR        | N/A

As covered by `ClassMetadataTest::testAddConstraintDoesNotAcceptValid`, this check is useless, as `Valid` already accepts only properties as targets.

This check is a [leftover of a time](9b07b0c) `Valid` was extending `Traverse` which was allowing classes & properties.
The `Valid` targets are properly checked by the lines above, the same way as other constraints.

Commits
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0086562 [Validator] Remove specific check for Valid targets

src/Symfony/Component/Validator/Mapping/ClassMetadata.php

@@ -14,7 +14,6 @@
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\Constraints\GroupSequence;
 use Symfony\Component\Validator\Constraints\Traverse;
-use Symfony\Component\Validator\Constraints\Valid;
 use Symfony\Component\Validator\Exception\ConstraintDefinitionException;
 use Symfony\Component\Validator\Exception\GroupDefinitionException;
 
@@ -183,10 +182,6 @@ public function addConstraint(Constraint $constraint)
             throw new ConstraintDefinitionException(sprintf('The constraint "%s" cannot be put on classes.', \get_class($constraint)));
         }
 
-        if ($constraint instanceof Valid) {
-            throw new ConstraintDefinitionException(sprintf('The constraint "%s" cannot be put on classes.', \get_class($constraint)));
-        }
-
         if ($constraint instanceof Traverse) {
             if ($constraint->traverse) {
                 // If traverse is true, traversal should be explicitly enabled