Drop useless guard condition

Apparently it was added in a08bc3b to
satisfy Psalm. Either there was an issue with that version of Psalm or
more helpful phpdoc was added to upstream packages, which makes this
code block redundant.

Mapping/ClassMetadataFactory.php

@@ -5,7 +5,6 @@
 use Doctrine\ORM\Id\AbstractIdGenerator;
 use Doctrine\ORM\Mapping\ClassMetadata;
 use Doctrine\ORM\Mapping\ClassMetadataFactory as BaseClassMetadataFactory;
-use Doctrine\ORM\Mapping\ClassMetadataInfo;
 
 use function assert;
 
@@ -18,10 +17,6 @@ protected function doLoadMetadata($class, $parent, $rootEntityFound, array $nonS
     {
         parent::doLoadMetadata($class, $parent, $rootEntityFound, $nonSuperclassParents);
 
-        if (! $class instanceof ClassMetadataInfo) {
-            return;
-        }
-
         $customGeneratorDefinition = $class->customGeneratorDefinition;
 
         if (! isset($customGeneratorDefinition['instance'])) {