flake.lock: Update (#420)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/f021fdc7493b0243129a979fd338eaae50a931ef?narHash=sha256-9/BfieHsR0BC5LaQr1WvqBBcfNAOMHHUpgV31NRZWf4%3D' (2024-11-25)
  → 'github:nix-community/neovim-nightly-overlay/c868a93ed4dcb19861474661d3f8cf5b8bbb01d2?narHash=sha256-S6LcEOdbc5YlHDXJvCH5H03DNuBwrLBkRic%2BEQrmd/8%3D' (2024-11-26)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/ff00d583af8f1ce21a508d701d09c54d2621b16e?narHash=sha256-ctSHOjNaWQM6g5L2OhJyEMTeMYEbIGk2vENqhT8FWbs%3D' (2024-11-24)
  → 'github:neovim/neovim/66bb1e577c96d8eb63c04dcc737394b4ce2b0f5d?narHash=sha256-2vEA6SuddlQh6agDXTk2Um1NSSxcXzLmErOUdJ9ffGE%3D' (2024-11-25)

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