flake: update inputs

[github-actions[bot]]

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

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/e36e9f57337d0ff0cf77aceb58af4c805472bfae?narHash=sha256-OpX0StkL8vpXyWOGUD6G%2BMA26wAXK6SpT94kLJXo6B4%3D' (2024-07-27)
  → 'github:NixOS/nixpkgs/81610abc161d4021b29199aa464d6a1a521e0cc9?narHash=sha256-TcXjLVNd3VeH1qKPH335Tc4RbFDbZQX%2Bd7rqnDUoRaY%3D' (2024-08-02)

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