nixos/etc: remove assertion

          assertion = lib.versionAtLeast config.boot.kernelPackages.kernel.version "6.6";

          message = "`system.etc.overlay.enable requires a newer kernel, at least version 6.6";

        }

        {

          assertion = config.systemd.sysusers.enable -> (config.users.mutableUsers == config.system.etc.overlay.mutable);

          message = ''

            When using systemd-sysusers and mounting `/etc` via an overlay, users

            can only be mutable when `/etc` is mutable and vice versa.

          '';

        }

      ];

      boot.initrd.availableKernelModules = [ "loop" "erofs" "overlay" ];