flake.lock: Update (#106)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:neovim/neovim/aa62579a684277d86b1f4a7588464e0ec4227b94?dir=contrib' (2023-10-15)
  → 'github:neovim/neovim/0a3505eb9df8d57a9a0bcecf02bb3dda1c8edd29?dir=contrib' (2023-10-15)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/01441e14af5e29c9d27ace398e6dd0b293e25a54' (2023-10-11)
  → 'github:nixos/nixpkgs/12bdeb01ff9e2d3917e6a44037ed7df6e6c3df9d' (2023-10-15)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>