flake.lock: Update (#979)

Flake lock file updates:

• Updated input 'nixos-infra':
    'github:NixOS/infra/b2cb376a37b84e82c9a2dd16a575a02b445b8b41?narHash=sha256-K6kHtWGrfXPanulpREHEnW6AmN9BhHbU7k3BeOmtMQA%3D' (2025-07-11)
  → 'github:NixOS/infra/07c76d89f710b4f5ad8cb49eb8156ca08a2d21eb?narHash=sha256-UxcB/hwSJ1sVwfJrA7xJyi/h99dGmILi0TXH2HZXan4%3D' (2025-07-19)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/9807714d6944a957c2e036f84b0ff8caf9930bc0?narHash=sha256-LwWRsENAZJKUdD3SpLluwDmdXY9F45ZEgCb0X%2BxgOL0%3D' (2025-07-08)
  → 'github:NixOS/nixpkgs/6e987485eb2c77e5dcc5af4e3c70843711ef9251?narHash=sha256-RKwfXA4OZROjBTQAl9WOZQFm7L8Bo93FQwSJpAiSRvo%3D' (2025-07-16)

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

Author: github-actions[bot]