Update flake.lock

[graham33]

Automated changes by the update-flake-lock GitHub Action.

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/7c9cc5a6e5d38010801741ac830a3f8fd667a7a0' (2023-10-19)
  → 'github:NixOS/nixpkgs/19cbff58383a4ae384dea4d1d0c823d72b49d614' (2023-11-22)

Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force