chore(deps): update actions/checkout action to v6 (#485)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://redirect.github.com/actions/checkout) |
action | major | `v2` → `v6` |

---

### Release Notes

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

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

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

### [`v5`](https://redirect.github.com/actions/checkout/compare/v4...v5)

[Compare
Source](https://redirect.github.com/actions/checkout/compare/v4...v5)

###
[`v4`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v422)

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

- `url-helper.ts` now leverages well-known environment variables by
[@&#8203;jww3](https://redirect.github.com/jww3) in
[#&#8203;1941](https://redirect.github.com/actions/checkout/pull/1941)
- Expand unit test coverage for `isGhes` by
[@&#8203;jww3](https://redirect.github.com/jww3) in
[#&#8203;1946](https://redirect.github.com/actions/checkout/pull/1946)

###
[`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>

---

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---

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---

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.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
         shell: ${{ matrix.platform.shell }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v4
         with: