update nixpkgs

bitcoin: 30.2 -> 31.0
bitcoind: 30.2 -> 31.0
clboss: 0.15.1 -> 0.16.0
clightning: 25.12.1 -> 26.04.1
elementsd: 23.3.2 -> 23.3.3
lightning-loop: 0.31.5-beta -> 0.33.0-beta

lightning-loop 0.31.7+ blocks until lnd's chain notifier is ready
(lightninglabs/loop@bde49d7a), so the workaround sleep added in the
previous commit is no longer needed for lightning-loop. The
lightning-pool workaround stays — pool has no equivalent fix and
isn't actively maintained.

Note: nbxplorer test fails (presumed incompatibility with bitcoin 31).

modules/lightning-loop.nix

@@ -128,8 +128,6 @@ in {
       requires = [ "lnd.service" ];
       after = [ "lnd.service" "nix-bitcoin-secrets.target" ];
       serviceConfig = nbLib.defaultHardening // {
-        # TODO: temporary sleep to prevent race condition
-        ExecStartPre = "${pkgs.coreutils}/bin/sleep 5";
         ExecStart = "${cfg.package}/bin/loopd --configfile=${configFile}";
         User = lnd.user;
         Restart = "on-failure";