minor #11549 Add missing ";" to use statement (thePhrenologist)

This PR was submitted for the master branch but it was merged into the 4.2 branch instead (closes #11549).

Discussion
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Add missing ";" to use statement

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Commits
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dee67b5 Update security.rst

Author: OskarStark

best_practices/security.rst

@@ -356,7 +356,7 @@ via the even easier shortcut in a controller::
         $this->denyAccessUnlessGranted('edit', $post);
 
         // use Symfony\Component\Security\Core\Exception\AccessDeniedException;
-        // use Symfony\Component\Security\Core\Authorization\AuthorizationCheckerInterface
+        // use Symfony\Component\Security\Core\Authorization\AuthorizationCheckerInterface;
         //
         // ...
         //