flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/ff7b65b44d01cf9ba6a71320833626af21126384' (2023-09-12)
  → 'github:numtide/flake-utils/4022d587cbbfd70fe950c1e2083a02621806a725' (2023-12-04)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/886c9aee6ca9324e127f9c2c4e6f68c2641c8256' (2023-12-18)
  → 'github:NixOS/nixpkgs/d6863cbcbbb80e71cecfc03356db1cda38919523' (2023-12-21)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/20fd62b0891707a1db8117d09fc3e65a1cd0f6d7' (2023-12-19)
  → 'github:oxalica/rust-overlay/b8c487832712f4e3e6f9e81b70e6654eb907abfc' (2023-12-22)
• Updated input 'sops-nix':
    'github:Mic92/sops-nix/e19071f9958c8da4f4347d3d78790d97e98ba22f' (2023-12-02)
  → 'github:Mic92/sops-nix/f7db64b88dabc95e4f7bee20455f418e7ab805d4' (2023-12-18)
• Updated input 'sops-nix/nixpkgs-stable':
    'github:NixOS/nixpkgs/dfb95385d21475da10b63da74ae96d89ab352431' (2023-11-25)
  → 'github:NixOS/nixpkgs/a19a71d1ee93226fd71984359552affbc1cd3dc3' (2023-12-17)
• Updated input 'treefmt-nix':
    'github:numtide/treefmt-nix/e82f32aa7f06bbbd56d7b12186d555223dc399d1' (2023-11-12)
  → 'github:numtide/treefmt-nix/2961375283668d867e64129c22af532de8e77734' (2023-12-19)