nix: update flake.lock

[github-actions]

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

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/bfa9810ff7104a17555ab68ebdeafb6705f129b1?narHash=sha256-QyhimDBaDBtMfRc7kyL28vo%2BHTwXRPq3hz%2BBgSJDotw%3D' (2025-03-21)
  → 'github:NixOS/nixpkgs/507b63021ada5fee621b6ca371c4fca9ca46f52c?narHash=sha256-jhZDfXVKdD7TSEGgzFJQvEEZ2K65UMiqW5YJ2aIqxMA%3D' (2025-04-23)

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