Add scheduler.alpha.kubernetes.io/critical-pod annotation

Signed-off-by: Chirayu Kapoor <dev.csociety@gmail.com>

content/en/docs/reference/labels-annotations-taints/_index.md

@@ -747,6 +747,16 @@ created from a VolumeSnapshot.
 Refer to [Converting the volume mode of a Snapshot](/docs/concepts/storage/volume-snapshots/#convert-volume-mode)
 and the [Kubernetes CSI Developer Documentation](https://kubernetes-csi.github.io/docs/) for more information.
 
+### scheduler.alpha.kubernetes.io/critical-pod (deprecated)
+
+Example: `scheduler.alpha.kubernetes.io/critical-pod: ""`
+
+Used on: Pod
+
+This annotation lets Kubernetes control plane know about a pod being a critical pod so that the descheduler will not remove this pod.
+
+{{< note >}} Starting in v1.16, this annotation was removed in favor of [Pod Priority](/docs/concepts/scheduling-eviction/pod-priority-preemption/). {{< /note >}}
+
 ## Annotations used for audit
 
 <!-- sorted by annotation -->