Add a comment to valkey. (#4783)

### What problem does this PR solve?
#4775

### Type of change

- [x] Documentation Update

docker/docker-compose-base.yml

@@ -114,6 +114,7 @@ services:
     restart: on-failure
 
   redis:
+    # swr.cn-north-4.myhuaweicloud.com/ddn-k8s/docker.io/valkey/valkey:8
     image: valkey/valkey:8
     container_name: ragflow-redis
     command: redis-server --requirepass ${REDIS_PASSWORD} --maxmemory 128mb --maxmemory-policy allkeys-lru