minor #12076 Fix use of deprecated Symfony\Bridge\Doctrine\RegistryInterface (Tobion)

This PR was merged into the 4.3 branch.

Discussion
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Fix use of deprecated Symfony\Bridge\Doctrine\RegistryInterface

See symfony/symfony#32817

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Commits
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7719400 Fix use of deprecated Symfony\Bridge\Doctrine\RegistryInterface

Author: OskarStark

doctrine.rst

@@ -669,11 +669,11 @@ But what if you need a more complex query? When you generated your entity with
 
     use App\Entity\Product;
     use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
-    use Symfony\Bridge\Doctrine\RegistryInterface;
+    use Doctrine\Common\Persistence\ManagerRegistry;
 
     class ProductRepository extends ServiceEntityRepository
     {
-        public function __construct(RegistryInterface $registry)
+        public function __construct(ManagerRegistry $registry)
         {
             parent::__construct($registry, Product::class);
         }
@@ -691,7 +691,7 @@ a new method for this to your repository::
     // ...
     class ProductRepository extends ServiceEntityRepository
     {
-        public function __construct(RegistryInterface $registry)
+        public function __construct(ManagerRegistry $registry)
         {
             parent::__construct($registry, Product::class);
         }