Specify ZFS datasets dependencies for each service

modules/communication.nix

@@ -91,7 +91,7 @@ in {
       signal = {
         port = 8338;
         format = "mautrix-python";
-        package = latest-mautrix-signal;
+        package = mautrix-signal;
         serviceConfig = {
           StateDirectory = [ "matrix-as-signal" "signald" ];
           JoinNamespaceOf = "signald.service";