minor symfony#51831 [Notifier] Fix failing testcase (OskarStark)

This PR was merged into the 6.4 branch.

Discussion
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[Notifier] Fix failing testcase

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | symfony#51276
| License       | MIT

Follows
* symfony#51276

Commits
-------

f7384f4 [Notifier] Fix failing testcase

Author: nicolas-grekas

src/Symfony/Component/Notifier/Tests/Message/NullMessageTest.php

@@ -30,10 +30,7 @@ public function testCanBeConstructed(MessageInterface $message)
         $this->assertSame($message->getSubject(), $nullMessage->getSubject());
         $this->assertSame($message->getRecipientId(), $nullMessage->getRecipientId());
         $this->assertSame($message->getOptions(), $nullMessage->getOptions());
-
-        (null === $message->getTransport())
-            ? $this->assertSame('null', $nullMessage->getTransport())
-            : $this->assertSame($message->getTransport(), $nullMessage->getTransport());
+        $this->assertSame($message->getTransport(), $nullMessage->getTransport());
     }
 
     public static function messageDataProvider(): \Generator