flake.lock: Update (#320)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/314e12ba369ccdb9b352a4db26ff419f7c49fa84?narHash=sha256-5fNndbndxSx5d%2BC/D0p/VF32xDiJCJzyOqorOYW4JEo%3D' (2024-12-13)
  → 'github:NixOS/nixpkgs/1c6e20d41d6a9c1d737945962160e8571df55daa?narHash=sha256-GIMyMt1pkkoXdCq9un859bX6YQZ/iYtukb9R5luazLM%3D' (2024-12-20)
• Updated input 'unstable-pkgs':
    'github:NixOS/nixpkgs/3566ab7246670a43abd2ffa913cc62dad9cdf7d5?narHash=sha256-AKU6qqskl0yf2%2BJdRdD0cfxX4b9x3KKV5RqA6wijmPM%3D' (2024-12-13)
  → 'github:NixOS/nixpkgs/d70bd19e0a38ad4790d3913bf08fcbfc9eeca507?narHash=sha256-4EVBRhOjMDuGtMaofAIqzJbg4Ql7Ai0PSeuVZTHjyKQ%3D' (2024-12-19)

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