add comment re calendar time

modules/services/deployerbot/default.nix

@@ -71,6 +71,12 @@
         systemd.timers.deployerbot = {
           description = "deployerbot-main timer";
           wantedBy = ["timers.target"];
+          # such nixpkgs commits:
+          #
+          #     Merge release-23.05 into staging-next-23.05
+          #
+          # happen at around 00:15 UTC. This is *probably* what
+          # we want to follow.
           timerConfig.OnCalendar = "*-*-* 00:30:00 UTC";
         };