rename mathjax-config.js to force the browsers to reload

layouts/partials/site_js.html

@@ -2,7 +2,7 @@
 
     {{/* Config LaTeX math rendering. */}}
     {{ if or .Params.math site.Params.math }}
-    {{ $mathjax_config := resources.Get "js/mathjax-config.js" }}
+    {{ $mathjax_config := resources.Get "js/mathjax3-config.js" }}
     <script src="{{ $mathjax_config.RelPermalink }}"></script>
     {{ end }}