chore: format everything

This implicates a change from nixpkgs-fmt to nixfmt. Nixfmt will become
the new standard on nix formatting, sanctioned by the nixpkgs. To verify
that these changes are purely in whitespace, but not semantic:

git diff --ignore-all-space -w HEAD^!

That will only show newline changes, make the diffing somewhat easier.

Signed-off-by: wucke13 <wucke13+github@gmail.com>

util/Cargo.toml

@@ -25,6 +25,5 @@ mio = { workspace = true }
 tempfile = { workspace = true }
 uds = { workspace = true, optional = true, features = ["mio_1xx"] }
 
-
 [features]
 experiment_file_descriptor_passing = ["uds"]