Minor docs update

[patrick-nicodemus]

https://github.com/haskell/ghcup-hs/edit/master/docs/steps.md

In the section:

*Where to go from here
*
How to learn Haskell proper
To learn Haskell, try any of those:

A beginner friendly 4-lectures course with exercises (by Dmitrii Kovanikov)

• The link to Dmitrii Kovanikov's personal website is broken.
• The linked lecture course contains a warning that it is no longer maintained.

The first of these should be fixed, the latter is less important but perhaps there is material available which is currently maintained.

[hasufell]

@chshersh what is the fixed link?

[chshersh]

@hasufell This is the correct link: https://chshersh.com/

[Bodigrim]

• The linked lecture course contains a warning that it is no longer maintained.

It's unmaintained in a very narrow sense: the content has got stable and the author no longer reviews solutions. Pretty much every course and textbook are "unmaintained" in this way.