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

Csp/ContentSecurityPolicyHandler.php

@@ -180,9 +180,7 @@ private function generateNonce(): string
      */
     private function generateCspHeader(array $directives): string
     {
-        return array_reduce(array_keys($directives), function ($res, $name) use ($directives) {
-            return ('' !== $res ? $res.'; ' : '').sprintf('%s %s', $name, implode(' ', $directives[$name]));
-        }, '');
+        return array_reduce(array_keys($directives), fn ($res, $name) => ('' !== $res ? $res.'; ' : '').sprintf('%s %s', $name, implode(' ', $directives[$name])), '');
     }
 
     /**

Tests/Controller/ProfilerControllerTest.php

@@ -188,9 +188,7 @@ public function testReturns404onTokenNotFound($withCsp)
         $profiler
             ->expects($this->exactly(2))
             ->method('loadProfile')
-            ->willReturnCallback(function ($token) {
-                return 'found' == $token ? new Profile($token) : null;
-            })
+            ->willReturnCallback(fn ($token) => 'found' == $token ? new Profile($token) : null)
         ;
 
         $controller = $this->createController($profiler, $twig, $withCsp);

Tests/Resources/IconTest.php

@@ -34,6 +34,6 @@ public function testIconFileContents($iconFilePath)
 
     public function provideIconFilePaths()
     {
-        return array_map(function ($filePath) { return (array) $filePath; }, glob(__DIR__.'/../../Resources/views/Icon/*.svg'));
+        return array_map(fn ($filePath) => (array) $filePath, glob(__DIR__.'/../../Resources/views/Icon/*.svg'));
     }
 }