Update constants.xml

Co-authored-by: Jordi Kroon <jordi@jordikroon.nl>

Author: lacatoire

reference/filter/constants.xml

@@ -163,7 +163,7 @@
    </term>
    <listitem>
     <simpara>
-     Throw a <classname>Filter\FilterFailedException</classname> when a
+     Throws a <exceptionname>Filter\FilterFailedException</exceptionname> when a
      validation filter fails, instead of returning &false;.
     </simpara>
     <simpara>