edit mathjax note

Author: archmoj

README.md

@@ -85,11 +85,9 @@ While non-minified source files may contain characters outside UTF-8, it is reco
 
 > Please note that as of v2 the "plotly-latest" outputs (e.g. https://cdn.plot.ly/plotly-latest.min.js) will no longer be updated on the CDN, and will stay at the last v1 patch v1.58.4. Therefore, to use the CDN with plotly.js v2 and higher, you must specify an exact plotly.js version.
 
-### To support MathJax
-Load relevant MathJax (v2) files *Before* the plotly.js script tag:
+To support MathJax, you need to load version two of MathJax e.g. `v2.7.5` files from CDN or npm.
 ```html
 <script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-AMS-MML_SVG.js"></script>
-<script src="https://cdn.plot.ly/plotly-2.0.0-rc.3.min.js"></script>
 ```
 
 ## Bundles