flake.lock: Update (#68)

Automated changes by the
[update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock)
GitHub Action.

```
Flake lock file updates:

• Updated input 'home-manager':
    'github:nix-community/home-manager/97d7946b5e107dd03cc82f21165251d4e0159655?narHash=sha256-igllW0yG%2BUbetvhT11jnt9RppSHXYgMykYhZJeqfHs0%3D' (2025-01-18)
  → 'github:nix-community/home-manager/4481a16d1ac5bff4a77c608cefe08c9b9efe840d?narHash=sha256-rk/cmrvq3In0TegW9qaAxw%2B5YpJhRWt2p74/6JStrw0%3D' (2025-01-21)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/5df43628fdf08d642be8ba5b3625a6c70731c19c?narHash=sha256-Tbk1MZbtV2s5aG%2BiM99U8FqwxU/YNArMcWAv6clcsBc%3D' (2025-01-16)
  → 'github:NixOS/nixpkgs/9e4d5190a9482a1fb9d18adf0bdb83c6e506eaab?narHash=sha256-nmKOgAU48S41dTPIXAq0AHZSehWUn6ZPrUKijHAMmIk%3D' (2025-01-21)
```

### 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:

```sh
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
```

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