[FrameworkBundle] Fix mailer config with XML

[lyrixx]

Q	A
Branch?	5.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Issues
License	MIT

I noticed that, while adding test for #54044

---

Before my patch, if I keep only one recipients:

>…ome/gregoire/dev/github.com/lyrixx/symfony(5.4 *) git di
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Fixtures/xml/mailer_with_dsn.xml b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Fixtures/xml/mailer_with_dsn.xml
index be53f59bc3..5ccdefaf32 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Fixtures/xml/mailer_with_dsn.xml
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Fixtures/xml/mailer_with_dsn.xml
@@ -11,7 +11,7 @@
             <framework:envelope>
                 <framework:sender>sender@example.org</framework:sender>
                 <framework:recipients>redirected@example.org</framework:recipients>
-                <framework:recipients>redirected1@example.org</framework:recipients>
+                <!-- <framework:recipients>redirected1@example.org</framework:recipients> -->
             </framework:envelope>
             <framework:header name="from">from@example.org</framework:header>
             <framework:header name="bcc">bcc1@example.org</framework:header>
>…ome/gregoire/dev/github.com/lyrixx/symfony(5.4 *) ./phpunit src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/XmlFrameworkExtensionTest.php --filter 'testMailer#0'
PHPUnit 9.6.16 by Sebastian Bergmann and contributors.

Warning:       Your XML configuration validates against a deprecated schema.
Suggestion:    Migrate your XML configuration using "--migrate-configuration"!

Testing Symfony\Bundle\FrameworkBundle\Tests\DependencyInjection\XmlFrameworkExtensionTest
E                                                                   1 / 1 (100%)R

Time: 00:00.103, Memory: 21.88 MB

There was 1 error:

1) Symfony\Bundle\FrameworkBundle\Tests\DependencyInjection\XmlFrameworkExtensionTest::testMailer with data set #0 ('mailer_with_dsn', array('smtp://example.com'))
Symfony\Component\Config\Definition\Exception\InvalidTypeException: Invalid type for path "framework.mailer.envelope.recipients". Expected "array", but got "string"

And I cannot add more XML configuration, without this patch

[lyrixx]

Failures seems un-related