chore(deps): update actions/checkout action to v4 (#43)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://redirect.github.com/actions/checkout) |
action | major | `v2` -> `v4` |

---

### Release Notes

<details>
<summary>actions/checkout (actions/checkout)</summary>

###
[`v4`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v421)

[Compare
Source](https://redirect.github.com/actions/checkout/compare/v3...v4)

- Check out other refs/\* by commit if provided, fall back to ref by
[@&#8203;orhantoy](https://redirect.github.com/orhantoy) in
[https://github.com/actions/checkout/pull/1924](https://redirect.github.com/actions/checkout/pull/1924)

###
[`v3`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v360)

[Compare
Source](https://redirect.github.com/actions/checkout/compare/v2...v3)

- [Fix: Mark test scripts with Bash'isms to be run via
Bash](https://redirect.github.com/actions/checkout/pull/1377)
- [Add option to fetch tags even if fetch-depth >
0](https://redirect.github.com/actions/checkout/pull/579)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

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

♻ **Rebasing**: Whenever PR is behind base branch, 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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.github/workflows/crush-pics.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Crush images
         uses: crush-pics/crush-pics-github-action@master
         with: