Update to nixos 23.05

- Update using patch notes
- Remove etherpad which didn't work
- Remove code-server which depended on deprecated nodejs versions and was unused
- Remove pkgs-unstable
- Update nodejs to nodejs-20
diff --git a/modules/node.nix b/modules/node.nix
index d5f832f..0de7e98 100644
--- a/modules/node.nix
+++ b/modules/node.nix
@@ -1,6 +1,6 @@
 { config, pkgs, ... }: {
   environment.systemPackages = with pkgs; [
-    nodejs-19_x
+    nodejs_20
     nodePackages.typescript
     yarn
     nodePackages.pm2