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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - uses: pnpm/action-setup@v4
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
         with:
           node-version: 22
           # TODO/eventually: try using the cache again