bug #17702 [TwigBridge] forward compatibility with Yaml 3.1 (xabbuh)

This PR was submitted for the 3.0 branch but it was merged into the 2.3 branch instead (closes #17702).

Discussion
----------

[TwigBridge] forward compatibility with Yaml 3.1

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Commits
-------

047c195 [TwigBridge] forward compatibility with Yaml 3.1

src/Symfony/Bridge/Twig/Extension/YamlExtension.php

@@ -39,6 +39,10 @@ class YamlExtension extends \Twig_Extension
             $dumper = new YamlDumper();
         }
 
+        if (defined('Symfony\Component\Yaml\Yaml::DUMP_OBJECT')) {
+            $dumpObjects = (int) $dumpObjects;
+        }
+
         return $dumper->dump($input, $inline, 0, false, $dumpObjects);
     }