Update security.rst

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

Author: johnkrovitch

security.rst

@@ -692,7 +692,7 @@ The previous example only works if you have one authenticator in the firewall. I
 be retrieved from the request. If the current request is not under any firewall an ... exception will be thrown.
 
 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",
+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
 (ie `App\\Security\\Authenticator\\ExampleAuthenticator`)