Issue #3409549: New twig variable deprecation check should use a service and not the direct class

Closes #3409549

core/lib/Drupal/Core/Template/TwigNodeCheckDeprecations.php

@@ -37,7 +37,7 @@ public function compile(Compiler $compiler) {
       $usedNamesNode->addElement(new ConstantExpression($name, $this->getTemplateLine()));
     }
 
-    $compiler->write("\$this->env->getExtension('\Drupal\Core\Template\TwigExtension')\n");
+    $compiler->write("\$this->env->getExtension(\Drupal::service('twig.extension')::class)\n");
     $compiler->indent();
     $compiler->write("->checkDeprecations(\$context, ");
     $compiler->subcompile($usedNamesNode);