configure sphinx-init to use devel docs

[briantist]

sphinx-init currently still points to Ansible 4 docs for references that don't resolve in the current doc set.

We could point it at 5, and then update it as new ansible versions are released, but in my opinion the devel docs are the better ones to point to since what you're building with this process is probably going to be newer docs, pointing to the newest stuff.

@felixfontein recommended falling back to another version. Initially I agreed that was a good idea, but as I think about it more, I wonder if in the end it would cause references that are no longer valid in the latest docs to unexpectedly resolve to a previous version in the docs, hiding the error.

So I've included the fallback in this PR, but I think I'm leading toward removing it and using devel exclusively; open to discussion and thoughts as I'm not terribly knowledgeable on this stuff.

[felixfontein]

I now tend to agree that not referencing a fixed version is good. I would keep a comment which shows how to reference a specific version, but not mention one by default.

[felixfontein]

@briantist thanks!