flake.lock: Update Nixpkgs to fix static build

The problem was since switching to use libgit2, we had a package in our
closure (`http-parser`) that was always trying to build as a shared
object.

Underlying Nixpkgs PR (a 23.05 backport)
NixOS/nixpkgs#271202

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/9ba29e2346bc542e9909d1021e8fd7d4b3f64db0' (2023-11-13)
  → 'github:NixOS/nixpkgs/36c4ac09e9bebcec1fa7b7539cddb0c9e837409c' (2023-11-30)

flake.nix

@@ -1,7 +1,13 @@
 {
   description = "The purely functional package manager";
 
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.05-small";
+  # TODO Go back to nixos-23.05-small once
+  # https://github.com/NixOS/nixpkgs/pull/271202 is merged.
+  #
+  # Also, do not grab arbitrary further staging commits. This PR was
+  # carefully made to be based on release-23.05 and just contain
+  # rebuild-causing changes to packages that Nix actually uses.
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/staging-23.05";
   inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
   inputs.flake-compat = { url = "github:edolstra/flake-compat"; flake = false; };