[docs] Be consistent about how much information we include about elastic.co/guide

We have two guides on _where_ people can contribute to the docs: [Contribute locally](https://elastic.github.io/docs-builder/contribute/locally/) and [Contribute on the web](https://elastic.github.io/docs-builder/contribute/on-the-web/). In **Contribute on the web** we cover contributing to both elastic.co/guide AND elastic.co/docs. In **Contribute locally** we only cover elastic.co/docs.

How much information should we be including about elastic.co/guide in these docs? Should we limit the docs in docs-builder to information about docs-builder with notes that link off to other places for information about elastic.co/guide? Or should we document these processes side-by-side?