flake.lock: Update (#359)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/7d1c6f5314633cb52330dbfe26cb352ff14c295c?narHash=sha256-Y4L6/wzlhaTarOX15eVfIxzOG4EaebWHwjNW2EEBcGI%3D' (2024-09-16)
  → 'github:nix-community/neovim-nightly-overlay/90aaa1e9e6ff67b29840d357413f822056212c08?narHash=sha256-3iDVHqGq8mhP46XqIpepiURz4RJXwGUO0cHtplHhbX0%3D' (2024-09-17)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/78b85109338592c2bc89154278f2e961a14eee96?narHash=sha256-5UytTFcPk%2Bf1mCqSUV4kiYnu3ZopPs7aWiOBMvYtFW8%3D' (2024-09-15)
  → 'github:neovim/neovim/a0d8c2b86e788ce4273f0b8df258cd9e8e432d38?narHash=sha256-M2syKjdJH3uBCOAm9PZndNI46m6xGLXsOadUSen8wpY%3D' (2024-09-16)
• Updated input 'neovim-nightly/nixpkgs':
    'github:NixOS/nixpkgs/76d7694a3f681b0b750c01783df5d2177ef39fe7?narHash=sha256-EpiSl9nSINTmIW6MG6CulGwNAa6sHrBt8gQdyHUXzR4%3D' (2024-09-15)
  → 'github:NixOS/nixpkgs/20f9370d5f588fb8c72e844c54511cab054b5f40?narHash=sha256-MWTBH4dd5zIz2iatDb8IkqSjIeFum9jAqkFxgHLdzO4%3D' (2024-09-16)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/20f9370d5f588fb8c72e844c54511cab054b5f40?narHash=sha256-MWTBH4dd5zIz2iatDb8IkqSjIeFum9jAqkFxgHLdzO4%3D' (2024-09-16)
  → 'github:nixos/nixpkgs/658e7223191d2598641d50ee4e898126768fe847?narHash=sha256-zACxiQx8knB3F8%2BZe%2B1BpiYrI%2BCbhxyWpcSID9kVhkQ%3D' (2024-09-17)

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