minor #48793 Leverage arrow function syntax for closure (tigitz)

This PR was merged into the 6.3 branch.

Discussion
----------

Leverage arrow function syntax for closure

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #47658 <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->
| License       | MIT
| Doc PR        | <!-- required for new features -->

Rationale in the RFC [here](https://wiki.php.net/rfc/arrow_functions_v2#introduction)

It's also notable that using arrow function syntax rather than the classic one has been enforced in the past by symfony core member: symfony/symfony#48069 (comment)

So this PR would be consistent.

Commits
-------

f5802d3a2a Leverage arrow function syntax for closure

Author: nicolas-grekas

Transport/Connection.php

@@ -306,9 +306,7 @@ public function publish(string $body, array $headers = [], int $delayInMs = 0, A
      */
     public function countMessagesInQueues(): int
     {
-        return array_sum(array_map(function ($queueName) {
-            return $this->queue($queueName)->declareQueue();
-        }, $this->getQueueNames()));
+        return array_sum(array_map(fn ($queueName) => $this->queue($queueName)->declareQueue(), $this->getQueueNames()));
     }
 
     /**
@@ -494,12 +492,8 @@ public function channel(): \AMQPChannel
             if ('' !== ($this->connectionOptions['confirm_timeout'] ?? '')) {
                 $this->amqpChannel->confirmSelect();
                 $this->amqpChannel->setConfirmCallback(
-                    static function (): bool {
-                        return false;
-                    },
-                    static function (): bool {
-                        return false;
-                    }
+                    static fn (): bool => false,
+                    static fn (): bool => false
                 );
             }