fix: remove deprecated polyfill script

Author: timimm

mkdocs.yml

@@ -64,7 +64,6 @@ plugins:
       locale: en
 
 extra_javascript:
-  - https://polyfill.io/v3/polyfill.min.js?features=es6
   - https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js
 
 markdown_extensions: