treewide: Format all Nix files

Format all Nix files using the officially approved formatter,
making the CI check introduced in the previous commit succeed:

  nix-build ci -A fmt.check

This is the next step of the of the [implementation](https://github.com/NixOS/nixfmt/issues/153)
of the accepted [RFC 166](https://github.com/NixOS/rfcs/pull/166).

This commit will lead to merge conflicts for a number of PRs,
up to an estimated ~1100 (~33%) among the PRs with activity in the past 2
months, but that should be lower than what it would be without the previous
[partial treewide format](https://github.com/NixOS/nixpkgs/pull/322537).

Merge conflicts caused by this commit can now automatically be resolved while rebasing using the
[auto-rebase script](8616af08d9/maintainers/scripts/auto-rebase).

If you run into any problems regarding any of this, please reach out to the
[formatting team](https://nixos.org/community/teams/formatting/) by
pinging @NixOS/nix-formatting.

nixos/modules/services/networking/sniproxy.nix

@@ -1,4 +1,9 @@
-{ config, pkgs, lib, ... }:
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
 
 with lib;
 
@@ -14,7 +19,11 @@ let
 
 in
 {
-  imports = [ (mkRemovedOptionModule [ "services" "sniproxy" "logDir" ] "Now done by LogsDirectory=. Set to a custom path if you log to a different folder in your config.") ];
+  imports = [
+    (mkRemovedOptionModule [ "services" "sniproxy" "logDir" ]
+      "Now done by LogsDirectory=. Set to a custom path if you log to a different folder in your config."
+    )
+  ];
 
   options = {
     services.sniproxy = {