The passthru has been added to give a migration path, but those outputs
were not present on the 25.11's `nodejs` derivation. Removing those
is helpful to use them to discriminate between the slim and non-slim
variants for derivations that accept one or the other.
This was always equivalent to `nodejs-slim.src`.
This is a follow-up on https://github.com/NixOS/nixpkgs/pull/481461
which has links from a number of downstream projects that hit this.
