chore(ci): keep some docker images

.github/workflows/container-scan.yml

@@ -35,4 +35,4 @@ jobs:
         run: |
           docker buildx prune --filter=until=6h -f
           docker image rm meetup_trivy
-          docker system prune -af --volumes --filter=until=6h
+          docker system prune -af --volumes --filter=until=6h

.github/workflows/docker-build.yml

@@ -67,4 +67,4 @@ jobs:
       - name: Clean up Docker
         run: |
           docker buildx prune --filter=until=48h -f
-          docker system prune -af --volumes --filter=until=6h
+          docker system prune -af --volumes --filter=until=6h