flake.lock: Update (#153)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:neovim/neovim/089b934352437ab310a6dd3b138c7ed9445a3d7b?dir=contrib' (2023-12-22)
  → 'github:neovim/neovim/242261d4e77806cdb4559c2be58613113a393a4e?dir=contrib' (2023-12-23)
• Updated input 'neovim-nightly/flake-utils':
    'github:numtide/flake-utils/ff7b65b44d01cf9ba6a71320833626af21126384' (2023-09-12)
  → 'github:numtide/flake-utils/4022d587cbbfd70fe950c1e2083a02621806a725' (2023-12-04)

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