flake.lock: Update (#387)

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

```
Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/4633a7c72337ea8fd23a4f2ba3972865e3ec685d?narHash=sha256-2ThgXBUXAE1oFsVATK1ZX9IjPcS4nKFOAjhPNKuiMn0%3D' (2024-11-25)
  → 'github:nixos/nixpkgs/55d15ad12a74eb7d4646254e13638ad0c4128776?narHash=sha256-M1%2BuCoV5igihRfcUKrr1riygbe73/dzNnzPsmaLCmpo%3D' (2024-12-03)
```

### Running GitHub Actions on this PR

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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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