chore(deps): update actions/setup-node action to v6 (#164)

| datasource  | package            | from | to |
| ----------- | ------------------ | ---- | -- |
| github-tags | actions/setup-node | v5   | v6 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/release-please.yml

@@ -17,7 +17,7 @@ jobs:
       # TODO: googleapis/release-please-action cannot sign commits yet.
       #   We'll use the cli until there's a fix for
       #   https://github.com/googleapis/release-please/issues/2280.
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
         with:
           node-version: 24
       # TODO: remove bump-minor-pre-major when in production. It prevents