Update self-healing.md to include Deployment in controllers

It is important include the most widely used Kubernetes Resource(deployment) along with the other resources which are already mentioned in the document. It gives confidence to the new users and does not raise the concern if "deployment" is an exception.

Author: suhas-chikkanna

content/en/docs/concepts/architecture/self-healing.md

@@ -33,7 +33,7 @@ Here are some of the key components that provide Kubernetes self-healing:
 
 - **[kubelet](/docs/concepts/architecture/#kubelet):** Ensures that containers are running, and restarts those that fail.
 
-- **ReplicaSet, StatefulSet and DaemonSet controller:** Maintains the desired number of Pod replicas.
+- **Deployment, ReplicaSet, StatefulSet and DaemonSet controller:** Maintains the desired number of Pod replicas.
 
 - **PersistentVolume controller:** Manages volume attachment and detachment for stateful workloads.