fix(ops/machines/build01): stop using Nix 2.3 in CI

There's been a few deadlock problems with Nix 2.3, as discusssed in the
commit message of https://cl.tvl.fyi/c/depot/+/12334.

However, since the fork nothing prevents us from dropping the Nix 2.3
requirement for CI.

Change-Id: Ib00603597dbc11dc1b619fdeee264d7d519eaa02
Reviewed-on: https://cl.snix.dev/c/snix/+/30108
Autosubmit: Florian Klink <flokli@flokli.de>
Tested-by: besadii
Reviewed-by: Ryan Lahfa <masterancpp@gmail.com>

ops/machines/build01/default.nix

@@ -35,7 +35,6 @@ in
 
   boot.loader.initScript.enable = true;
   system.switch.enableNg = false;
-  nix.package = pkgs.nix_2_3;
   nix.nrBuildUsers = 256;
   nix.settings.max-jobs = 64;