minor #33868 Skip the intl notice if run with phpunit (jakzal)

This PR was squashed before being merged into the 5.0-dev branch (closes #33868).

Discussion
----------

Skip the intl notice if run with phpunit

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | Re #33825
| License       | MIT
| Doc PR        | -

Commits
-------

25461b358c Skip the intl notice if run with phpunit

Author: nicolas-grekas

DependencyInjection/FrameworkExtension.php

@@ -211,7 +211,7 @@ public function load(array $configs, ContainerBuilder $container)
                     ->addError('You cannot use the "slugger" service since the Translation contracts are not installed. Try running "composer require symfony/translation".');
             }
 
-            if (!\extension_loaded('intl')) {
+            if (!\extension_loaded('intl') && !\defined('PHPUNIT_COMPOSER_INSTALL')) {
                 @trigger_error('Please install the "intl" PHP extension for best performance.', E_USER_DEPRECATED);
             }
         }

Tests/Functional/SluggerLocaleAwareTest.php

@@ -16,6 +16,9 @@
  */
 class SluggerLocaleAwareTest extends AbstractWebTestCase
 {
+    /**
+     * @requires extension intl
+     */
     public function testLocalizedSlugger()
     {
         $kernel = static::createKernel(['test_case' => 'Slugger', 'root_config' => 'config.yml']);