Enable npm cache on setup-node action (#30577)

Enable npm dependency cache in
[setup-node](https://github.com/actions/setup-node). This should work
reliably and across branches as well.

.github/workflows/pull-e2e-tests.yml

@@ -24,6 +24,8 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: 20
+          cache: npm
+          cache-dependency-path: package-lock.json
       - run: make deps-frontend frontend deps-backend
       - run: npx playwright install --with-deps
       - run: make test-e2e-sqlite