[chore] flake.lock: update inputs

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/f4c846aee8e1e29062aa8514d5e0ab270f4ec2f9' (2024-09-08)
  → 'github:NixOS/nixpkgs/44a71ff39c182edaf25a7ace5c9454e7cba2c658' (2024-09-10)
• Updated input 'nixvim':
    'github:nix-community/nixvim/fc7e9b29271a03459191955f78d4128451b7cd81' (2024-09-10)
  → 'github:nix-community/nixvim/11c133e89e4090c43445a2c3b5af2322831d7219' (2024-09-11)
• Updated input 'unstable':
    'github:NixOS/nixpkgs/574d1eac1c200690e27b8eb4e24887f8df7ac27c' (2024-09-06)
  → 'github:NixOS/nixpkgs/1355a0cbfeac61d785b7183c0caaec1f97361b43' (2024-09-10)