Use Docker Hub credentials to avoid being rate-throttled (#20339)

.github/workflows/e2e-tests.yml

@@ -77,18 +77,30 @@ jobs:
         ports:
           - "80:80"
           - "25:25"
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
       postgres-sample:
         image: metabase/qa-databases:postgres-sample-12
         ports:
           - "5432:5432"
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
       mongo-sample:
         image: metabase/qa-databases:mongo-sample-4.0
         ports:
           - 27017:27017
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
       mysql-sample:
         image: metabase/qa-databases:mysql-sample-8
         ports:
           - 3306:3306
+        credentials:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
     steps:
     - uses: actions/checkout@v2
     - name: Prepare front-end environment