Update security.rst

Typo

Author: ThomasLandauer

reference/configuration/security.rst

@@ -568,7 +568,7 @@ logout_on_user_change
     The ``logout_on_user_change`` option was deprecated in Symfony 4.1.
 
 If ``false`` this option makes Symfony to not trigger a logout when the user has
-changed. Doing that is deprecated, so this option should set to ``true`` or
+changed. Doing that is deprecated, so this option should be set to ``true`` or
 unset to avoid getting deprecation messages.
 
 The user is considered to have changed when the user class implements