Bump actions/setup-node from 4 to 6 (#14)

Dependabot update merged after green checks.

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/setup-go@v7
         with:
           go-version-file: go.mod
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 24
       - run: node --test tests/chart.test.cjs