flake.lock: Update (#324)

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:nix-community/neovim-nightly-overlay/4b239d8da3a4888b660653dabec18bcc7cf70f7a?narHash=sha256-kNFdRdUvwTZOXt%2BmWCpb2Y99kqzAcBZqI/F/2fSjRJw%3D' (2024-08-14)
  → 'github:nix-community/neovim-nightly-overlay/34eea329cd65c65338d47134817b35e9b3ed10a4?narHash=sha256-3/LFSr3Nwrj0Weg9HPTGdK2WpWUhthG56PK6XGZ/L0M%3D' (2024-08-15)
• Updated input 'neovim-nightly/neovim-src':
    'github:neovim/neovim/9d74dc3ac5a66d0fd34de125476a92ec0a77ca58?narHash=sha256-u4XYsa9td3shTsiDftC7B%2BHnPgHgY78NeJHxHNkXxFs%3D' (2024-08-13)
  → 'github:neovim/neovim/615f7bbff06c0585aacce542fac4bc823070ebee?narHash=sha256-l8J6lQ7aZRWwQ2nCL5EGGeWT5viSZQSL6lYWcuSHZKY%3D' (2024-08-14)
• Updated input 'neovim-nightly/nixpkgs':
    'github:NixOS/nixpkgs/19674872444bb3e0768249e724d99c8649c3bd78?narHash=sha256-U5gKtbKuPahB02iGeGHFPlKr/HqrvSsHlEDEXoVyaPc%3D' (2024-08-13)
  → 'github:NixOS/nixpkgs/daf7bb95821b789db24fc1ac21f613db0c1bf2cb?narHash=sha256-VMg6N7MryOuvSJ8Sj6YydarnUCkL7cvMdrMcnsJnJCE%3D' (2024-08-14)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/daf7bb95821b789db24fc1ac21f613db0c1bf2cb?narHash=sha256-VMg6N7MryOuvSJ8Sj6YydarnUCkL7cvMdrMcnsJnJCE%3D' (2024-08-14)
  → 'github:nixos/nixpkgs/8b908192e64224420e2d59dfd9b2e4309e154c5d?narHash=sha256-nk0RaUB5f68BwtXAYy3WAjqFhVKqIl9Z89RGycTa2vk%3D' (2024-08-15)

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