Archive cfg-if repo

[clarfonthey]

Version of #2761 that just includes the cfg-if repo for now. This one has already had a new release and readme update to clarify it's unsupported.

[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/cfg-if':
      Archive
      Permission Changes:
        Removing team 'crate-maintainers''s maintain permission 
      Custom Properties:
          Removing 'crabwatch' (was 'true')