Renovate: actions/setup-python to v4 (#22)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-python](https://togithub.com/actions/setup-python) |
action | major | `v2` -> `v4` |

---

### Release Notes

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

### [`v4`](https://togithub.com/actions/setup-python/compare/v3...v4)

[Compare
Source](https://togithub.com/actions/setup-python/compare/v3...v4)

### [`v3`](https://togithub.com/actions/setup-python/compare/v2...v3)

[Compare
Source](https://togithub.com/actions/setup-python/compare/v2...v3)

</details>

---

### Configuration

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any time (no schedule defined).

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

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rebase/retry checkbox.

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

---

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this box

---

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.github/workflows/checks.yml

@@ -14,7 +14,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: set up python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: 3.9
 

.github/workflows/molecule.yml

@@ -25,7 +25,7 @@ jobs:
         with:
           path: "mirsg.postgresql"
       - name: Set up Python 3.9
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
         with:
           python-version: 3.9
       - name: Install test dependencies