flake.lock: Update

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:neovim/neovim/6823fdb20b1330142506410a62474166f646bf13?dir=contrib' (2023-10-07)
  → 'github:neovim/neovim/61f1e992ce984371a8d570c4dbb34ff759f5751a?dir=contrib' (2023-10-08)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/945559664c1dc5836173ee12896ba421d9b37181' (2023-10-07)
  → 'github:nixos/nixpkgs/5aabb5780a11c500981993d49ee93cfa6df9307b' (2023-10-08)
• Updated input 'pre-commit-hooks':
    'github:cachix/pre-commit-hooks.nix/66c352d33e0907239e4a69416334f64af2c685cc' (2023-10-05)
  → 'github:cachix/pre-commit-hooks.nix/8edf336c5ca85efe20004d076747f91b85a6d087' (2023-10-08)