chore: upgrade shell.nix

Author: leo-dur

shell.nix

@@ -1,12 +1,10 @@
 # Set up the project with nix
 # cf https://github.com/Kpler/ct-webserver#option-2-using-nix
 let
-  jdk = pkgs.openjdk11;
-
   nixpkgs = builtins.fetchTarball {
-    name   = "nixos-21.05";
-    url    = "https://github.com/NixOS/nixpkgs/archive/1f91fd104066.tar.gz";
-    sha256 = "1lcfcwgal9fpaiq71981abyzz160r6nx1y4pyy1dnvaf951xkdcj";
+    name   = "nixos-23.05-20230814";
+    url    = "https://github.com/NixOS/nixpkgs/archive/720e61ed8de1.tar.gz";
+    sha256 = "0ii10wmm8hqdp7bii7iza58rjaqs4z3ivv71qyix3qawwxx48hw9";
   };
 
   pkgs = import nixpkgs { };