Update, remove or document pl-tutorial

[Baltoli]

The PL tutorial is leading to confusion from external users who are unable to complete the lessons as written with modern K: #3698

We should do one of the following things:

• Update the lessons to reflect the current set of features supported by modern K
• Remove the broken code (rather than just dropping it silently from CI)
• Document externally that this tutorial is out of date and should not be relied on

[Baltoli]

Worth noting that we link to this content directly from the https://kframework.org/ landing page, so we really ought to resolve this one way or another.

[Baltoli]

@dwightguth favours the documentation option; we should also update the website homepage to reflect that. Best option as a stopgap

[Baltoli]

Is @grosu still using this code for anything teaching-related?

[QWYNG]

@Baltoli
Thank you for opening this issue!
Currently, is there any other documentation you would recommend for a beginning student to learn k?

[Baltoli]

https://kframework.org/k-distribution/k-tutorial/ The K tutorial is the best place to learn K as a programming language; the PL tutorial that you had the issue with is more of a reference for "how can I implement language X in K?

If you've finished the K tutorial, and would like some advice on using K in practice for a project, come and find us on Discord: https://discord.com/invite/CurfmXNtbN