servo: matrix-appservice-irc: decrease logging debug -> warn

hosts/by-name/servo/services/matrix/irc.nix

@@ -1,6 +1,5 @@
 # config docs:
 # - <https://github.com/matrix-org/matrix-appservice-irc/blob/develop/config.sample.yaml>
-#       probably want to remove that.
 { config, lib, ... }:
 
 let
@@ -128,6 +127,7 @@ in
     };
 
     ircService = {
+      logging.level = "warn";  # "error", "warn", "info", "debug"
       servers = {
         "irc.esper.net" = ircServer {
           name = "esper";