workflows: Update actions/checkout to v4.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

Author: andersk

.github/workflows/node.js.yml

@@ -10,6 +10,6 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - run: npm ci
       - run: npm test