[chore] flake.lock: update inputs

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/a9b86fc2290b69375c5542b622088eb6eca2a7c3' (2024-10-19)
  → 'github:NixOS/nixpkgs/89172919243df199fe237ba0f776c3e3e3d72367' (2024-10-20)
• Updated input 'nixvim':
    'github:nix-community/nixvim/0562e519ec0e69125c5edc917d41bccb54a534fd' (2024-10-21)
  → 'github:nix-community/nixvim/b076f006c6b0cc6644a651bd21d4449cc3e7e56d' (2024-10-22)
• Updated input 'treefmt-nix':
    'github:numtide/treefmt-nix/d986489c1c757f6921a48c1439f19bfb9b8ecab5' (2024-10-18)
  → 'github:numtide/treefmt-nix/aac86347fb5063960eccb19493e0cadcdb4205ca' (2024-10-22)
• Updated input 'unstable':
    'github:NixOS/nixpkgs/4c2fcb090b1f3e5b47eaa7bd33913b574a11e0a0' (2024-10-18)
  → 'github:NixOS/nixpkgs/1997e4aa514312c1af7e2bda7fad1644e778ff26' (2024-10-20)