Minor fix

Author: javiereguiluz

reference/configuration/security.rst

@@ -351,7 +351,7 @@ form_only
 
 Set this option to ``true`` to require that the login data is sent using a form
 (it checks that the request content-type is ``application/x-www-form-urlencoded``
-or ``multipart/form-data``) This is useful for example to prevent the.
+or ``multipart/form-data``). This is useful for example to prevent the
 :ref:`form login authenticator <security-form-login>` from responding to
 requests that should be handled by the :ref:`JSON login authenticator <security-json-login>`.