Fix wrong impression of browser stats

See this comment from a student: https://www.coursera.org/learn/html-css-javascript-for-web-developers/discussions/weeks/1/threads/YUiKu-cHEeadcAqQrKjg8A?sort=createdAtDesc

W3Schools does NOT show stats of regular users. It shows stats of users to THEIR site.

This point needs to be made clearer.