Update security.rst

Co-authored-by: Oskar Stark <[email protected]>

Author: johnkrovitch

security.rst

@@ -693,7 +693,7 @@ be retrieved from the request. If the current request is not under any firewall
 
 You can also pass the authenticator on which the user will
 be authenticated against. For built-in authenticators, you can pass an authenticator name like ``form_login``,
-"http_basic"... For custom authenticators, you can pass the service id of the authenticator
+``http_basic``... For custom authenticators, you can pass the service id of the authenticator
 (ie `App\\Security\\Authenticator\\ExampleAuthenticator`)
 
 .. code-block:: php