minor #3840 Suppress native return type deprecation msg (PhilETaylor)

This PR was merged into the 3.x branch.

Discussion
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Suppress native return type deprecation msg

> Method "Symfony\Component\DependencyInjection\Extension\ExtensionInterface::load()" might add "void" as a native return type declaration in the future. Do the same in implementation "Twig\Extra\TwigExtraBundle\DependencyInjection\TwigExtraExtension" now to avoid errors or add an explicit ``@return`` annotation to suppress this message.

Commits
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72d6f205 suppress native return type deprecation msg

extra/twig-extra-bundle/DependencyInjection/Compiler/MissingExtensionSuggestorPass.php

@@ -18,6 +18,7 @@ use Twig\Environment;
 
 class MissingExtensionSuggestorPass implements CompilerPassInterface
 {
+    /** @return void */
     public function process(ContainerBuilder $container)
     {
         if ($container->getParameter('kernel.debug')) {

extra/twig-extra-bundle/DependencyInjection/TwigExtraExtension.php

@@ -23,6 +23,7 @@ use Twig\Extra\TwigExtraBundle\Extensions;
  */
 class TwigExtraExtension extends Extension
 {
+    /** @return void */
     public function load(array $configs, ContainerBuilder $container)
     {
         $loader = new PhpFileLoader($container, new FileLocator(\dirname(__DIR__).'/Resources/config'));