flake.lock: Update

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:neovim/neovim/61f1e992ce984371a8d570c4dbb34ff759f5751a?dir=contrib' (2023-10-08)
  → 'github:neovim/neovim/c40a1c0f41ad2557b1e1e1850244eca2d895a07d?dir=contrib' (2023-10-10)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/5aabb5780a11c500981993d49ee93cfa6df9307b' (2023-10-08)
  → 'github:nixos/nixpkgs/2646b294a146df2781b1ca49092450e8a32814e1' (2023-10-08)
• Updated input 'pre-commit-hooks':
    'github:cachix/pre-commit-hooks.nix/8edf336c5ca85efe20004d076747f91b85a6d087' (2023-10-08)
  → 'github:cachix/pre-commit-hooks.nix/42e1b6095ef80a51f79595d9951eb38e91c4e6ca' (2023-10-09)