minor #35118 [DI] Removing unused variable (alirezamirsepassi)

This PR was submitted for the master branch but it was merged into the 5.0 branch instead.

Discussion
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[DI] Removing unused variable

| Q             | A
| ------------- | ---
| Branch?       | master <!-- see below -->
| Bug fix?      |no
| New feature?  |no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? |no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | - <!-- prefix each issue number with "Fix #", if any -->
| License       | MIT
| Doc PR        | - <!-- required for new features -->
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Commits
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12d3aa80ec Removing unused variable

src/Symfony/Component/DependencyInjection/TypedReference.php

@@ -20,7 +20,6 @@ class TypedReference extends Reference
 {
     private $type;
     private $name;
-    private $requiringClass;
 
     /**
      * @param string $id              The service identifier