chore(deps): bump actions/setup-node from 4 to 6

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 4 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@v4...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/evals-nightly.yml

@@ -41,7 +41,7 @@ jobs:
         uses: 'actions/checkout@v4' # ratchet:exclude
 
       - name: 'Set up Node.js'
-        uses: 'actions/setup-node@v4' # ratchet:exclude
+        uses: 'actions/setup-node@v6' # ratchet:exclude
         with:
           node-version: '20'
           cache: 'npm'
@@ -82,7 +82,7 @@ jobs:
         uses: 'actions/checkout@v4' # ratchet:exclude
 
       - name: 'Set up Node.js'
-        uses: 'actions/setup-node@v4' # ratchet:exclude
+        uses: 'actions/setup-node@v6' # ratchet:exclude
         with:
           node-version: '20'
           cache: 'npm'