bug #35616 [Workflow] Make method signature compatible with 4.4 (pbowyer)

This PR was squashed before being merged into the 5.0 branch (closes #35616).

Discussion
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[Workflow] Make method signature compatible with 4.4

| Q             | A
| ------------- | ---
| Branch?       | 5.0 <!-- see below -->
| Bug fix?      | yes
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | Fix #35615  <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!-- required for new features -->
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 - Never break backward compatibility (see https://symfony.com/bc).
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A method signature changed in a non-backwards-compatible way in 5.0.0 - and in only one class. This commit fixes that - and has been tested.

For full details see ticket #35615.

Commits
-------

474be9613b [Workflow] Make method signature compatible with 4.4

src/Symfony/Component/Workflow/Event/Event.php

@@ -60,7 +60,7 @@ class Event extends BaseEvent
         return $this->workflow->getName();
     }
 
-    public function getMetadata(string $key, object $subject)
+    public function getMetadata(string $key, $subject)
     {
         return $this->workflow->getMetadataStore()->getMetadata($key, $subject);
     }