nixos/prosody-filer: set proper SystemCallFilter

nixos/modules/services/web-apps/prosody-filer.nix

···
         LockPersonality = true;
         RemoveIPC = true;
         RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
-        SystemCallFilter = [ "@system-service" "~@privileged" "~@resources" ];
+        SystemCallFilter = [ "@system-service" "~@privileged" ];
       };
     };
   };