migrate mathjax support from v2/v3 to v3/v4

Author: emilykl

devtools/test_dashboard/index-mathjax3chtml.html

@@ -49,12 +49,7 @@
             options.format = svgDocument.inputJax[0].name;
             return svgDocument.convert(math, options);
           };
-          /*
-          MathJax.tex2svgPromise = (math, options = {}) => {
-            options.format = svgDocument.inputJax[0].name;
-            return mathjax.handleRetriesFor(() => svgDocument.convert(math, options));
-          };
-          */
+
           MathJax.svgStylesheet = () => svgOutput.styleSheet(svgDocument);
         }
       }

devtools/test_dashboard/index.html

@@ -27,7 +27,7 @@
   <!-- Update UI elements if strict mode is enabled -->
   <script src="./strict.js"></script>
 
-  <script src="../../node_modules/@plotly/mathjax-v2/MathJax.js?config=TeX-AMS-MML_SVG"></script>
+  <script src="../../node_modules/@plotly/mathjax-v4/tex-svg.js"></script>
   <script charset="utf-8" id="source" src="../../build/plotly.js"></script>
   <script charset="utf-8" src="../../build/test_dashboard-bundle.js"></script>
 </body>