Update xquery.xml

Allowing empty has been actually been supported since eXist-db/exist#763, released with eXist 3.0.

Author: joewiz

src/main/xar-resources/data/xquery/xquery.xml

@@ -106,9 +106,6 @@
                 <listitem>
                     <para>"count" clause</para>
                 </listitem>
-                <listitem>
-                    <para>"allowing empty" clause</para>
-                </listitem>
             </itemizedlist>
 
             <para>eXist-db supports all standard XQuery functions except for the following:</para>