This process was automated by [my fork of `nix-doc-munge`]; thanks
to @pennae for writing this tool! It automatically checks that the
resulting documentation doesn't change, although my fork loosens
this a little to ignore some irrelevant whitespace and typographical
differences.

As of this commit there is no DocBook remaining in the options
documentation.

You can play along at home if you want to reproduce this commit:

    $ NIX_PATH=nixpkgs=flake:nixpkgs/c1bca7fe84c646cfd4ebf3482c0e6317a0b13f22 \
      nix shell nixpkgs#coreutils \
      -c find . -name '*.nix' \
      -exec nix run github:emilazy/nix-doc-munge/0a7190f600027bf7baf6cb7139e4d69ac2f51062 \
      {} +

[my fork of `nix-doc-munge`]: https://github.com/emilazy/nix-doc-munge

These all use DocBook markup too complex for `nix-doc-munge` to handle,
have syntax that clashes with Markdown, or already contain Markdown
syntax that currently isn't rendering correctly.

Converting DocBook list syntax makes me think that maybe Markdown
isn't so bad after all.

This doesn't look like the hostname on my system, it has an extra unique prefix.