minor #29210 [Messenger] Fix typos (ogizanagi)

This PR was merged into the 4.2-dev branch.

Discussion
----------

[Messenger] Fix typos

| Q             | A
| ------------- | ---
| Branch?       | 4.2 <!-- see below -->
| Bug fix?      | no
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | N/A   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | N/A

Just small typos extracted from #29166 in case it doesn't make it to 4.2.

Commits
-------

7e763f96c1 [Messenger] Fix typos

Author: nicolas-grekas

DependencyInjection/FrameworkExtension.php

@@ -1583,7 +1583,7 @@ private function registerMessengerConfiguration(array $config, ContainerBuilder
             }, $messageConfiguration['senders']);
 
             $sendersId = 'messenger.senders.'.$message;
-            $sendersDefinition = $container->register($sendersId, RewindableGenerator::class)
+            $container->register($sendersId, RewindableGenerator::class)
                 ->setFactory('current')
                 ->addArgument(array(new IteratorArgument($senders)));
             $messageToSendersMapping[$message] = new Reference($sendersId);