doc: markdown dead link

I found some markdown dead link in CI:
```
FILE: docs/en/latest/deployments/ack.md
[✖] https://hub.kubeapps.com/charts/bitnami/etcd → Status: 502

7 links checked.

ERROR: 1 dead links found!
[✖] https://hub.kubeapps.com/charts/bitnami/etcd → Status: 502
```