chore(deps): update actions/setup-go action to v6 (#2092)

This PR contains the following updates:

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

---

### Release Notes

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

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

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

</details>

---

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are satisfied.

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---

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.github/workflows/openapi.yaml

@@ -55,7 +55,7 @@ jobs:
               run: npm run redoc:build:clean:yaml
 
             - name: Setup Go
-              uses: actions/setup-go@v5
+              uses: actions/setup-go@v6
               with:
                   go-version: "1.25"
                   # Disable caching since go.sum is gitignored and regenerated on each run.