HTML: remove MathJax 3 artifacts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: rbeezer

js/mathjaxknowl3.js

@@ -411,12 +411,6 @@ $inline-solution-back|$divisional-solution-back|$worksheet-solution-back|$readin
 <!-- HTML only, a developer must elect to use this CSS file -->
 <xsl:param name="debug.developer.css" select="'no'"/>
 
-<!-- HTML only, testing early-releases of MathJax 4                    -->
-<!-- See: https://github.com/mathjax/MathJax/releases                  -->
-<!-- https://github.com/mathjax/MathJax-src/releases/tag/4.0.0-alpha.1 -->
-<xsl:param name="debug.mathjax4" select="'no'"/>
-<xsl:variable name="mathjax4-testing" select="$debug.mathjax4 = 'yes'"/>
-
 <!-- A permanent string parameter to control the creation of  -->
 <!-- "View Source" knowls, which is a developer task, not a   -->
 <!-- publisher task (though it could be?).  So permanent, but -->