Remove the Kedro architecture page from the documentation

[stichbury]

Description

I don't see that the Kedro architecture page has much that is useful to contribute. It has less than 3000 page views in a year and I don't really know what it is documenting.

It may be that we need a way to illustrate the overall system, and perhaps a mermaid graphic (and then a reorganisation of the docs to reflect that graphic) would be a good way to do it. However, I don't see what we have as valuable and suggest that we remove it. Maybe we could write a blog post about the architecture of Kedro at a later stage.

[astrojuanlu]

I think we should put this, and possibly other pages, in a Developers Documentation site, that is more for contributors (even for ourselves). This is what we did at RtD, see https://docs.readthedocs.io/ vs https://dev.readthedocs.io/ (and discussion at readthedocs/readthedocs.org#8751)

[astrojuanlu]

(Alternatively we could opt for something completely different for the dev docs, for example using the GitHub wiki)