chore(deps): update actions/setup-go action to v6 (#22)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [actions/setup-go](https://github.com/actions/setup-go) | action | major | `v5` -> `v6` |

---

### Release Notes

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

### [`v6`](https://github.com/actions/setup-go/compare/v5...v6)

[Compare Source](https://github.com/actions/setup-go/compare/v5...v6)

</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:eyJjcmVhdGVkSW5WZXIiOiI0MS45OC40IiwidXBkYXRlZEluVmVyIjoiNDEuOTguNCIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOltdfQ==-->

Reviewed-on: #22
Reviewed-by: t.behrendt <t.behrendt@noreply.localhost>
Co-authored-by: Renovate Bot <renovate@t00n.de>
Co-committed-by: Renovate Bot <renovate@t00n.de>

.gitea/workflows/ci.yaml

@@ -12,7 +12,7 @@ jobs:
       - linux_amd64
     steps:
       - uses: actions/checkout@v4
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@v6
         with:
           go-version-file: go.mod
       - run: make test