style: Switch to nixfmt from nixpkgs-fmt

Most of the ecosystem has moved to this formatter,
and many people configured their editors to autoformat it with this formatter.

Closes: https://git.snix.dev/snix/snix/issues/62
Change-Id: Icf39e7836c91fc2ae49fbe22a40a639105bfb0bd
Reviewed-on: https://cl.snix.dev/c/snix/+/30671
Reviewed-by: Florian Klink <flokli@flokli.de>
Tested-by: besadii
Autosubmit: Ilan Joselevich <personal@ilanjoselevich.com>

ops/modules/o11y/loki.nix

@@ -1,6 +1,7 @@
-{ config
-, lib
-, ...
+{
+  config,
+  lib,
+  ...
 }:
 let
   cfg = config.services.depot.loki;
@@ -38,7 +39,10 @@ in
           ring = {
             kvstore.store = "memberlist";
             # TODO: Such a ugly hack.
-            instance_interface_names = [ "enp1s0" "lo" ];
+            instance_interface_names = [
+              "enp1s0"
+              "lo"
+            ];
           };
           replication_factor = 1;
         };