Update or remove the 12factor app reference

[aheusingfeld]

12factor app is a sample of a company deciding for what shall be Macro Architecture aspects. Yet, as their flight level varies they are not exactly the best example. If we don't find a better example in the wild, we should rather remove them.

[ewolff]

There is https://isa-principles.org/

[mikesperber]

I'm all for removing it.

[mrtnlhmnn]

Yes, agree. Let's get rid of it. (If a training still wants to mention it, this does not harm, but it should not be a "must have" in the curriculum