Remove cache-polyfill.js from the article

[mkbctrl]

Hey, while reading your article here:
https://developers.google.com/web/fundamentals/codelabs/offline/

I've visited the repo in order to take a look at the cache-polyfill and was suprised I found it only in Removal commit message. Maybe it would be good to remove it from the code provided in the article as well.