Update flake.lock

[github-actions]

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

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/a0c9e3aee1000ac2bfb0e5b98c94c946a5d180a9?narHash=sha256-icE1IJE9fHcbDfJ0%2BqWoDdcBXUoZCcIJxME4lMHwvSM%3D' (2024-04-12)
  → 'github:NixOS/nixpkgs/b3fcfcfabd01b947a1e4f36622bbffa3985bdac6?narHash=sha256-iJYnKMtLi5u6hZhJm94cRNSDG5Rz6ZzIkGbhPFtDRm0%3D' (2024-05-15)

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