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](actions/setup-node@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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -77,7 +77,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
 
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
         with:
           cache: npm
           cache-dependency-path: src/Elastic.Documentation.Site/package-lock.json