chore(deps): update actions/checkout action to v4 (#24)

This PR contains the following updates:

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

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### Release Notes

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

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

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

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

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

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

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

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
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Reviewed-on: #24
Co-authored-by: Renovate Bot <renovate@brmartin.co.uk>
Co-committed-by: Renovate Bot <renovate@brmartin.co.uk>

.github/workflows/build.yaml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Set up JDK 17
         uses: actions/setup-java@v4

.github/workflows/release.yaml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Set up JDK 17
         uses: actions/setup-java@v4