upgrade PaymentServer

nixos/pkgs/zkapissuer/repo.nix

@@ -2,6 +2,6 @@
 fetchFromGitHub {
   owner = "PrivateStorageio";
   repo = "PaymentServer";
-  rev = "2ca189c51a5314eb476d1866d28ee483701af6f5";
-  sha256 = "1sb53lvi6alwdjhx4cv1gg7ywkqf18n1zjgdj3nigq3vjwxhdcpb";
+  rev = "ff30e85c231a3b5ad76426bbf8801f8f76884367";
+  sha256 = "1spz19f5z96shmfpazj0rv6877xvchf3gl49a4xahjbbsz39x34x";
 }