minor symfony#53542 [ErrorHandler] Fix RecursiveDirectoryIterator exception with wrong composer autoload (symfonyaml)

This PR was squashed before being merged into the 5.4 branch.

Discussion
----------

[ErrorHandler] Fix `RecursiveDirectoryIterator` exception with wrong composer autoload

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | yes
| Issues        | Fix symfony#53541
| License       | MIT

### Issue
When defining an autoload directory in `composer.json` that actually points to a file _(rather than a directory)_, we have the following error :
```
Uncaught UnexpectedValueException: RecursiveDirectoryIterator::__construct(/path/to/file):
Failed to open directory: Not a directory
```
See all details and how to reproduce it in the issue symfony#53541

### Solution
In this PR :
 - Make sure that the [ClassNotFoundErrorEnhancer::findClassInPath()](https://github.com/symfony/error-handler/blob/7.0/ErrorEnhancer/ClassNotFoundErrorEnhancer.php#L108) method checks if the `$path` is a directory.
- Fixed coding standards proposed by fabbot.io

Commits
-------

7809765 [ErrorHandler] Fix `RecursiveDirectoryIterator` exception with wrong composer autoload

Author: nicolas-grekas

src/Symfony/Component/ErrorHandler/ErrorEnhancer/ClassNotFoundErrorEnhancer.php

@@ -21,9 +21,6 @@
  */
 class ClassNotFoundErrorEnhancer implements ErrorEnhancerInterface
 {
-    /**
-     * {@inheritdoc}
-     */
     public function enhance(\Throwable $error): ?\Throwable
     {
         // Some specific versions of PHP produce a fatal error when extending a not found class.
@@ -110,7 +107,8 @@ private function getClassCandidates(string $class): array
 
     private function findClassInPath(string $path, string $class, string $prefix): array
     {
-        if (!$path = realpath($path.'/'.strtr($prefix, '\\_', '//')) ?: realpath($path.'/'.\dirname(strtr($prefix, '\\_', '//'))) ?: realpath($path)) {
+        $path = realpath($path.'/'.strtr($prefix, '\\_', '//')) ?: realpath($path.'/'.\dirname(strtr($prefix, '\\_', '//'))) ?: realpath($path);
+        if (!$path || !is_dir($path)) {
             return [];
         }