treewide: switch back to pkgs.nix

checks/installation/flake-module.nix

@@ -18,16 +18,6 @@ let
         pkgs.bubblewrap
       ] ++ builtins.map (i: i.outPath) (builtins.attrValues self.inputs);
       closureInfo = pkgs.closureInfo { rootPaths = dependencies; };
-      # with Nix 2.24 we get:
-      # vm-test-run-test-installation> installer # error: sized: unexpected end-of-file
-      # vm-test-run-test-installation> installer # error: unexpected end-of-file
-      # This seems to be fixed with Nix 2.26
-      # Remove this line once `pkgs.nix` is 2.26+
-      nixPackage =
-        assert
-          lib.versionOlder pkgs.nix.version "2.26"
-          && lib.versionAtLeast pkgs.nixVersions.latest.version "2.26";
-        pkgs.nixVersions.latest;
     in
     {
       imports = [
@@ -49,7 +39,6 @@ let
       # both installer and target need to use the same diskImage
       virtualisation.diskImage = "./target.qcow2";
       virtualisation.memorySize = 3048;
-      nix.package = nixPackage;
       nix.settings = {
         substituters = lib.mkForce [ ];
         hashed-mirrors = null;

pkgs/clan-cli/default.nix

@@ -166,14 +166,7 @@ pythonRuntime.pkgs.buildPythonApplication {
             buildInputs = [
               pkgs.bash
               pkgs.coreutils
-              # looks like Nix 2.26 fixes the profile creation race condition we were running into on Nix 2.24
-              # Switch this back to `pkgs.nix` when `pkgs.nix` is Nix 2.26+
-              (
-                assert
-                  lib.versionOlder pkgs.nix.version "2.26"
-                  && lib.versionAtLeast pkgs.nixVersions.latest.version "2.26";
-                pkgs.nixVersions.latest
-              )
+              pkgs.nix
             ];
             closureInfo = pkgs.closureInfo {
               rootPaths = [