Docs: is the 'Package not Found?' section still needed?

[liammcdermott]

The documentation says:

#### Package not Found?

The package has only been added to nixpkgs recently. In case you're using an older nixpkgs version, the package might not be available yet. In that case you can install `ihp-new` like this:

\```bash
nix-env -f https://downloads.digitallyinduced.com/ihp-new.tar.gz -i ihp-new
\```

I'm thinking ihp-new has been in nixpkgs for a while, and this section can be deleted. Any objections?

[mpscholten]

Agree, let's remove it 👍 If there's multiple people running into that problem in the future, we could re-add it again.