Spell the source correctly

nixos/pkgs/zkapissuer.nix

 { fetchFromGitHub, callPackage }:
 let
   paymentServer = fetchFromGitHub {
-    owner = "PrivateStorage";
+    owner = "PrivateStorageio";
     repo = "PaymentServer";
     rev = "6fbaac7a14d2a03b74e10a4a82b1147ee1dd7d49";
     sha256 = "0z8mqmns3fqbjy765830s5q6lhz3lxmslxahjc155jsv5b46gjip";