minor #22861 Close PHP code in phpt file (keradus)

This PR was merged into the 3.3 branch.

Discussion
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Close PHP code in phpt file

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes-ish
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | n/a
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

that's the only phpt file that is not closing php code section
this causes linting via `php -l` to fail

Commits
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36f6e05 Close PHP code in phpt file

src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/weak_vendors_on_vendor.phpt

@@ -17,6 +17,8 @@ require PHPUNIT_COMPOSER_INSTALL;
 require_once __DIR__.'/../../bootstrap.php';
 require __DIR__.'/fake_vendor/autoload.php';
 require __DIR__.'/fake_vendor/acme/lib/deprecation_riddled.php';
+
+?>
 --EXPECTF--
 Unsilenced deprecation notices (2)