Bump actions/setup-node from 5 to 6

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 5 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](https://github.com/actions/setup-node/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build-on-pull-request.yml

@@ -52,7 +52,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Use Node.js
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: '20.x'
       - run: cd docs && npm ci

.github/workflows/publish-docs.yml

@@ -40,7 +40,7 @@ jobs:
 
       - uses: actions/checkout@v5
       - name: Use Node.js
-        uses: actions/setup-node@v5
+        uses: actions/setup-node@v6
         with:
           node-version: '20.x'
       - run: cd docs && npm ci