`-h` (short help) still shows the same.
This gates it behind an `unstable-v4` feature flag to avoid disrupting users who set the help without knowing where all it shows up (particularly derive users where `ArgEnum` is automatically extracting the help).
Fixes#3312
I was working to drop the active features across all crates, so that
when cargo unified them during `--workspace`, we'd get this for free.
Alas, it looks like its not happening.