DOC: Update documentation with correct link
Fixed from shttp to https in docs link

You are doing a PR against the 0.20.x branch. Can you do it against master? @jorisvandenbossche You changed the branch. Do you need me to do anything else? Yes, I tried, but that apparently does not work (many other commits are then included). You can also do that, but then you need to rebase on latest master? @jorisvandenbossche : The PR has been fixed to be against `master` now. Thanks!