Resolves: fdo#74820 Failed to recognized Heading 6-Export to MediaWiki

See http://www.mediawiki.org/wiki/Help:Formatting

Change-Id: I6cf50e957d3aef6bff6e86a031da175d5544e98c

swext/mediawiki/src/filter/odt2mediawiki.xsl

@@ -296,14 +296,14 @@
 		Function generating a wiki heading prefix.
 		
 		@param level
-			The heading level. The value must be between 1 and 5.
+			The heading level. The value must be between 1 and 6.
 	-->
 	<template name="mk-heading-prefix">
 		<param name="level"/>
 		<choose>
-			<when test="$level &gt; 5">
+			<when test="$level &gt; 6">
 				<call-template name="mk-heading-prefix">
-					<with-param name="level" select="5"/>
+					<with-param name="level" select="6"/>
 				</call-template>
 			</when>
 			<when test="$level &gt; 0">