Revert "Switching to use of mathjax v4"

This reverts commit d5380c2.

Author: linev

modules/base/latex.mjs

@@ -1085,12 +1085,12 @@ async function loadMathjax() {
          }
       };
 
-      let mj_dir = '../mathjax/4.0.0';
+      let mj_dir = '../mathjax/3.2.0';
       if (browser.webwindow && source_dir.indexOf('https://root.cern/js') < 0 && source_dir.indexOf('https://jsroot.gsi.de') < 0)
          mj_dir = 'mathjax';
 
-      return loadScript(source_dir + mj_dir + '/tex-svg.js')
-               .catch(() => loadScript('https://cdn.jsdelivr.net/npm/mathjax@4/tex-svg.js'))
+      return loadScript(source_dir + mj_dir + '/es5/tex-svg.js')
+               .catch(() => loadScript('https://cdn.jsdelivr.net/npm/mathjax@3.2.0/es5/tex-svg.js'))
                .then(() => promise);
    }