Remove comment

This is only semi correct. We keep logs up to what's specified in the privacy
policy.  Currently, that is implemented as keeping them for up to 30 days on
the individual nodes as well as on the central Loki server.

nixos/modules/monitoring/exporters/promtail.nix

@@ -34,10 +34,6 @@ in {
     services.promtail.enable = true;
     networking.firewall.interfaces.monitoringvpn.allowedTCPPorts = [ 9080 ];
 
-    # Since we'll send our journald logs elsewhere, we don't need to keep them
-    # here for very long.  Keep them for a *little* while just to provide some
-    # context in case someone ends up looking at the logs on the system itself
-    # but generally suppose that people will look at Loki instead.
     services.journald.extraConfig = ''
       # This tells journald it can discard log files that contain only log
       # entries older than...