chore(deps): Update actions/setup-python action to v6 (#42)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-python](https://redirect.github.com/actions/setup-python) | action | major | `v5` -> `v6` |

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### Release Notes

<details>
<summary>actions/setup-python (actions/setup-python)</summary>

### [`v6`](https://redirect.github.com/actions/setup-python/compare/v5...v6)

[Compare Source](https://redirect.github.com/actions/setup-python/compare/v5...v6)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - Between 12:00 AM and 03:59 AM, on day 1 of the month ( * 0-3 1 * * ) (UTC), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

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Author: cq-bot

.github/workflows/lint.yml

@@ -14,7 +14,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - name: Install dependencies

.github/workflows/unittests.yml

@@ -19,7 +19,7 @@ jobs:
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - name: Install dependencies