Apply to router.default

Using a `chain_router` usually replaces the `router` and add the `router.default` to it's chain.

This would `addExpressionLanguageProvider` to the default router only as the chain router is not expected to have `addExpressionLanguageProvider` as it is not part of the router interface.

See #37042

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/AddExpressionLanguageProvidersPass.php

@@ -28,8 +28,8 @@ class AddExpressionLanguageProvidersPass implements CompilerPassInterface
     public function process(ContainerBuilder $container)
     {
         // routing
-        if ($container->has('router')) {
-            $definition = $container->findDefinition('router');
+        if ($container->has('router.default')) {
+            $definition = $container->findDefinition('router.default');
             foreach ($container->findTaggedServiceIds('routing.expression_language_provider', true) as $id => $attributes) {
                 $definition->addMethodCall('addExpressionLanguageProvider', [new Reference($id)]);
             }