minor #47401 Replace get_class() calls by ::class (deguif)

This PR was squashed before being merged into the 6.2 branch.

Discussion
----------

Replace get_class() calls by ::class

| Q             | A
| ------------- | ---
| Branch?       | 6.2
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Replace `get_class()` by `::class`

Commits
-------

675601b8f7 Replace get_class() calls by ::class

Author: fabpot

Requirement/EnumRequirement.php

@@ -38,7 +38,7 @@ public function __construct(string|array $cases = [])
                     throw new InvalidArgumentException(sprintf('Case must be a "BackedEnum" instance, "%s" given.', get_debug_type($case)));
                 }
 
-                $class ??= \get_class($case);
+                $class ??= $case::class;
 
                 if (!$case instanceof $class) {
                     throw new InvalidArgumentException(sprintf('"%s::%s" is not a case of "%s".', get_debug_type($case), $case->name, $class));