Add back dockerhub login

Author: Weves

.github/workflows/pr-playwright-tests.yml

@@ -134,6 +134,15 @@ jobs:
         id: login-ecr
         uses: aws-actions/amazon-ecr-login@v2
 
+      # needed for pulling Vespa, Redis, Postgres, and Minio images
+      # otherwise, we hit the "Unauthenticated users" limit
+      # https://docs.docker.com/docker-hub/usage/
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_TOKEN }}
+
       - name: Pull Docker images
         run: |
           # Pull all images from ECR in parallel