flake.lock: Update

[github-actions[bot]]

Automated changes by the update-flake-lock GitHub Action.

Flake lock file updates:

• Updated input 'defaultChannel':
    'github:NixOS/nixpkgs/1d9c2c9b3e71b9ee663d11c5d298727dace8d374?narHash=sha256-8MUgifkJ7lkZs3u99UDZMB4kbOxvMEXQZ31FO3SopZ0%3D' (2024-07-19)
  → 'github:NixOS/nixpkgs/68c9ed8bbed9dfce253cc91560bf9043297ef2fe?narHash=sha256-Tybxt65eyOARf285hMHIJ2uul8SULjFZbT9ZaEeUnP8%3D' (2024-07-21)

Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force