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

Author: renovate[bot]

.github/workflows/validate.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-node@v4
+    - uses: actions/setup-node@v6
       with:
         node-version-file: '.nvmrc'
     - run: make validate.ci