Page 404 error

[ingenious452]

In doc/intro/learning.rst the link to the "Problem Solving with Algorithms and Data Structures" shows a 404 error after checking, It seems that the site is no longer availabel at that link.

[joshagilend]

I had this problem too!

I wonder if anyone else had this element lost in their page. 404.

[vaariable]

Seems like this link is down, possibly the entire site too.
I'll try to make a pull request with an alternative equivalent to fix this soon