Revert upgrade to more recent checkout action in GitHub action

Author: gomander

.github/workflows/firebase-hosting-push.yml

@@ -16,7 +16,10 @@ jobs:
       PUBLIC_FIREBASE_MEASUREMENT_ID: '${{ secrets.PUBLIC_FIREBASE_MEASUREMENT_ID }}'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
       - name: Install depedencies
         run: npm install
       - name: Run unit tests