chore(deps): update actions/checkout action to v4 (#19)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/checkout](https://github.com/actions/checkout) | action | major | `v3` -> `v4` |

---

### Release Notes

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

### [`v4`](https://github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v400)

[Compare Source](actions/checkout@v3...v4)

-   [Support fetching without the --progress option](actions/checkout#1067)
-   [Update to node20](actions/checkout#1436)

</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).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNi43OS4xIiwidXBkYXRlZEluVmVyIjoiMzYuNzkuMSIsInRhcmdldEJyYW5jaCI6Im1haW4ifQ==-->

Reviewed-on: https://gitea.com/gitea/terraform-provider-gitea/pulls/19
Co-authored-by: Renovate Bot <renovate-bot@gitea.com>
Co-committed-by: Renovate Bot <renovate-bot@gitea.com>

.github/workflows/release.yml

@@ -15,7 +15,7 @@ jobs:
     steps:
       -
         name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       -
         name: Unshallow
         run: git fetch --prune --unshallow