Clarify the RFC lifecycle; make sure to remove all the references to "active" and "complete" folders

[nodakai]

README.md still refers to the "complete" folder which no longer exists. All the references to "active" and "complete" folders should be removed in accordance with the change #367 by @pnkfelix .

That also means we will have to update 0002-rfc-process.md. However Issue #360 proposes to consistently use the PR page of an RFC as its URI (sort of.) Since a PR page refers to the snapshot of the cloned repo at the time of merging, it will be confusing to update the merged RFC file. As far as I know, merged RFC files were updated only for filling out metadata and for making typographical changes, so the divergences haven't caused any problems so far.

[Centril]

I believe this is moot now; closing therefore.