New CLI manpages don't disclaim its experimental nature

[cole-h]

Describe the bug

As the title states, running nix build --help (or man nix3-build) does not mention its experimental nature anywhere.

Steps To Reproduce

1. Run nix build --help
2. Observe lack of EXPERIMENTAL warnings

Expected behavior

Unless I missed the new CLI being moved out of experimental status (entirely possible), I'd expect there to be a prominent warning about the experimental nature of the new nix CLI.

nix-env --version output

nix-env (Nix) 2.4pre20210209_ee3846b

Additional context

The EXPERIMENTAL text was removed in b159d23.

[cole-h]

Thanks!