flake.lock: Update (#442)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/1bac49debd490fc69306e117c6da95a523bd7c35?narHash=sha256-Q8E0fL3BLA1qxNIZZEbb3IAGYucqyUYe/rrmzjGrEkc%3D' (2024-12-19)
  → 'github:nix-community/neovim-nightly-overlay/57e5021f82590f4c6ac0a220ac8787bc28e0a94d?narHash=sha256-hXt72ZmJeu7gv3cCIEDwY892xe0U9bin6LIXwjXlQ7U%3D' (2024-12-21)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/02bc40c19401ea9f7529cbc81bd18bd01c39bb3c?narHash=sha256-lFSBvz6gLvOE%2B7HXt6H9MrMBHlznMluUb1JbAJQwdA4%3D' (2024-12-18)
  → 'github:neovim/neovim/e1c2179dd93ed2cd787b1cd016606b1901a1acfe?narHash=sha256-isblUJ6somE7siX9YVZuy6FNLJTBtkgK1shmEqrm7dI%3D' (2024-12-20)
• Updated input 'neovim-nightly/treefmt-nix':
    'github:numtide/treefmt-nix/76159fc74eeac0599c3618e3601ac2b980a29263?narHash=sha256-/QceWozrNg915Db9x/Ie5k67n9wKgGdTFng%2BZ1Qw0kE%3D' (2024-12-18)
  → 'github:numtide/treefmt-nix/65712f5af67234dad91a5a4baee986a8b62dbf8f?narHash=sha256-MMi74%2BWckoyEWBRcg/oaGRvXC9BVVxDZNRMpL%2B72wBI%3D' (2024-12-20)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>