chore(deps): update actions/setup-go action to v6 (#52)

This PR contains the following updates:

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

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### 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>

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### 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.

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 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

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Reviewed-on: #52
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

@@ -15,7 +15,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v5
       - name: Setup go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version-file: go.mod
           check-latest: true