minor symfony#59798 [DoctrineBridge] Fix deprecation with doctrine/dbal ^4.3 (alexandre-daubois)

This PR was merged into the 6.4 branch.

Discussion
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[DoctrineBridge] Fix deprecation with `doctrine/dbal` ^4.3

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

Fixes deprecations raised by doctrine/dbal#6787.

Commits
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b1d5de5 [DoctrineBridge] Fix deprecation with `doctrine/dbal` ^4.3

Author: nicolas-grekas

src/Symfony/Bridge/Doctrine/Tests/Fixtures/SingleAssociationToIntIdEntity.php

@@ -14,13 +14,15 @@
 use Doctrine\ORM\Mapping\Column;
 use Doctrine\ORM\Mapping\Entity;
 use Doctrine\ORM\Mapping\Id;
+use Doctrine\ORM\Mapping\JoinColumn;
 use Doctrine\ORM\Mapping\OneToOne;
 
 #[Entity]
 class SingleAssociationToIntIdEntity
 {
     public function __construct(
         #[Id, OneToOne(cascade: ['ALL'])]
+        #[JoinColumn(nullable: false)]
         protected SingleIntIdNoToStringEntity $entity,
 
         #[Column(nullable: true)]