Update to PHP 8

test/Unit/Serializer/JsonSerializerTest.php

@@ -13,9 +13,7 @@ final class JsonSerializerTest extends AbstractTestCase
         $string = 'myString';
         $array = [0 => '1', 1 => '2', 2 => '3'];
 
-        $this->assertInternalType('string', $serializer->serialize($array));
         $this->assertEquals($string, $serializer->serialize($string));
-
         $this->assertEquals($array, $serializer->deserialize($serializer->serialize($array)));
     }