minor #10518 fixed use statement (OskarStark)

This PR was merged into the 4.1 branch.

Discussion
----------

fixed use statement

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/roadmap for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `master` for features of unreleased versions).

-->

Commits
-------

9cdd4ad fixed use statement

Author: javiereguiluz

security.rst

@@ -701,7 +701,7 @@ If you need to get the logged in user from a service, use the
     // src/Service/ExampleService.php
     // ...
 
-    use Symfony\\Component\\Security\\Core\\Security;
+    use Symfony\Component\Security\Core\Security;
 
     class ExampleService
     {