Use the path option in systemd instead of repeating pkgs

nixos/modules/services/misc/duckdns.nix

@@ -49,6 +49,11 @@ in
       after = [ "network.target" ];
       wantedBy = [ "multi-user.target" ];
       startAt = "*:0/5";
+      path = [
+        pkgs.gnused
+        pkgs.systemd
+        pkgs.curl
+      ];
       serviceConfig = {
         Type = "simple";
         LoadCredential = [
@@ -57,14 +62,14 @@ in
         DynamicUser = true;
       };
       script = ''
-        export DUCKDNS_TOKEN=$(${pkgs.systemd}/bin/systemd-creds cat DUCKDNS_TOKEN_FILE)
+        export DUCKDNS_TOKEN=$(systemd-creds cat DUCKDNS_TOKEN_FILE)
         ${lib.optionalString (cfg.domains != null) ''
           export DUCKDNS_DOMAINS='${lib.strings.concatStringsSep "," cfg.domains}'
             ''}
       ${lib.optionalString (cfg.domainsFile != null) ''
-        export DUCKDNS_DOMAINS=$(${pkgs.systemd}/bin/systemd-creds cat DUCKDNS_DOMAINS_FILE | ${pkgs.gnused}/bin/sed -z 's/\n/,/g')
+        export DUCKDNS_DOMAINS=$(systemd-creds cat DUCKDNS_DOMAINS_FILE | sed -z 's/\n/,/g')
           ''}
-      ${pkgs.curl}/bin/curl --no-progress-meter -k "https://www.duckdns.org/update?domains=$DUCKDNS_DOMAINS&token=$DUCKDNS_TOKEN&ip=" | grep -v "KO"
+      curl --no-progress-meter -k "https://www.duckdns.org/update?domains=$DUCKDNS_DOMAINS&token=$DUCKDNS_TOKEN&ip=" | grep -v "KO"
         '';
     };
   };