update workflow

Author: EleanorWho

.github/workflows/backend_ci.yml

@@ -72,5 +72,4 @@ jobs:
       - name: Build and Push Docker Image to ECR
         run: |
           docker build -t ${{ secrets.ECR_REPO }}:latest .
-          docker tag ${{ secrets.ECR_REPO }}:latest ${{ secrets.ECR_REPO }}:latest
           docker push ${{ secrets.ECR_REPO }}:latest