Remove malicious polyfill.io dependency in the docs

Author: fizruk

mkdocs.yml

@@ -61,7 +61,6 @@ theme:
 
 extra_javascript:
   - javascript/mathjax.js
-  - https://polyfill.io/v3/polyfill.min.js?features=es6
   - https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js
 
 plugins: