chore: update flake lock file (#54)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/5c24cf2f0a12ad855f444c30b2421d044120c66f?narHash=sha256-XtTSSIB2DA6tOv%2Bl0FhvfDMiyCmhoRbNB%2B0SeInZkbk%3D' (2024-04-19)
  → 'github:nixos/nixpkgs/63c3a29ca82437c87573e4c6919b09a24ea61b0f?narHash=sha256-4cPymbty65RvF1DWQfc%2BBc8B233A1BWxJnNULJKQ1EY%3D' (2024-05-02)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Jon Seager <jon@sgrs.uk>