Update registerphpfunctions.xml Fix typo (#4358)

Author: mmalferov

reference/xsl/xsltprocessor/registerphpfunctions.xml

@@ -62,7 +62,7 @@
       <entry>8.4.0</entry>
       <entry>
        It is now possible to use <type>callable</type>s for callbacks
-       when using <parameter>restrict</parameter> with <type>array</type>
+       when using <parameter>functions</parameter> with <type>array</type>
        entries.
       </entry>
      </row>