"ArviZ in Context" link appears twice in the side bar

[star1327p]

"ArviZ in Context" link appears twice in the side bar. It belongs to either User Guide or Tutorials, but not both.

[aloctavodia]

Not sure where to place it. "EABM" is clearly different from the rest ("explanation" in terms of https://diataxis.fr) so it makes sense to have it under a different title. But at the same time, not sure if make sense to have a category with just one member. Additionally, in arviz-stats and arviz-plots we have "user guide" and "tutorial", but in arviz-base we just have "tutorials". We should unify that.

[OriolAbril]

I think we can get rid of the tutorial section for now. As we grow the docs and we can separate them into the diataxis categories better. I also added the "architecture" section inside "Reference" but it is more explanation than reference. We can start with upper half (tutorials+howto) in "user guide"; lower half in the other section (we can think of a better title too if we want otherwise we keep reference)